Name: setting limits on supersymmetry using simplified models
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The authors would like to thank Jay Wacker for significant discussion of simplified models and potential pitfalls. Many thanks also to Max Baak and Till Eifert for constructive criticism and encouragement whenever it was necessary. Thanks to the CERN Summer Student Program for making this collaboration possible.

1. Model Deconstruction
<ol>
	<li>Generate proton-proton collision events covering a plane in the parameter space of the NPM. Any event generator configuration that includes a parton shower and hadronization model can be used. In the case of MSUGRA for example, the mass spectra are generated using Isasugra33, and the branching fractions and decay widths are calculated using MSSMCalc34. For the event generation itself, MadGraph 5 1.3.934 with CTEQ 6L1 parton density functions35</sup...

<ol>
	<li>Miyazawa, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Baryon+Number+Changing+Currents.">Baryon Number Changing Currents.</a> Prog. Theor. Phys. 36, 1266-1276 (1966).</li><li>Ramond, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual+Theory+for+Free+Fermions.">Dual Theory for Free Fermions.</a> Phys. Rev. D. 3, 2415-2418 (1971).</li><li>Gol'fand, Y. A., Likhtman, E. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extension+of+the+Algebra+of+Poincare+Group+Generators+and+Violation+of+P+invariance.">Extension of the Algebra of Poincare Group Generators and Violation of P invariance.</a> JETP Lett. 13, 323-326 (1971).</li><li>Neveu, A., Schwarz, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Factorizable+dual+model+of+pions.">Factorizable dual model of pions.</a> Nucl. Phys. B. 31, 86-112 (1971).</li><li>Gervais, J. L., Sakita, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Field+theory+interpretation+of+supergauges+in+dual+models.">Field theory interpretation of supergauges in dual models.</a> Nucl. Phys. B. 34, 632-639 (1971).</li><li>Neveu, A., Schwarz, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quark+Model+of+Dual+Pions.">Quark Model of Dual Pions.</a> Phys. Rev. D. 4, 1109-1111 (1971).</li><li>Volkov, D. V., Akulov, V. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+the+neutrino+a+goldstone+particle.">Is the neutrino a goldstone particle.</a> Phys. Lett. B. 46, 109-110 (1973).</li><li>Wess, J., Zumino, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+lagrangian+model+invariant+under+supergauge+transformations.">A lagrangian model invariant under supergauge transformations.</a> Phys. Lett. B. 49, 52-54 (1974).</li><li>Wess, J., Zumino, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supergauge+transformations+in+four+dimensions.">Supergauge transformations in four dimensions.</a> Nucl. Phys. B. 70, 39-50 (1974).</li><li>Fayet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supersymmetry+and+Weak,+Electromagnetic+and+Strong+Interactions.">Supersymmetry and Weak, Electromagnetic and Strong Interactions.</a> Phys. Lett. B. 64, 159-162 (1976).</li><li>Fayet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneously+Broken+Supersymmetric+Theories+of+Weak,+Electromagnetic+and+Strong+Interactions.">Spontaneously Broken Supersymmetric Theories of Weak, Electromagnetic and Strong Interactions.</a> Phys. Lett. B. 69, 489-494 (1977).</li><li>Farrar, G. R., Fayet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phenomenology+of+the+Production,+Decay,+and+Detection+of+New+Hadronic+States+Associated+with+Supersymmetry.">Phenomenology of the Production, Decay, and Detection of New Hadronic States Associated with Supersymmetry.</a> Phys. Lett. B. 76, 575-579 (1978).</li><li>Fayet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relations+Between+the+Masses+of+the+Superpartners+of+Leptons+and+Quarks,+the+Goldstino+Couplings+and+the+Neutral+Currents.">Relations Between the Masses of the Superpartners of Leptons and Quarks, the Goldstino Couplings and the Neutral Currents.</a> Phys. Lett. B. 84, 416-420 (1979).</li><li>Dimopoulos, S., Georgi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Softly+Broken+Supersymmetry+and+SU(5.">Softly Broken Supersymmetry and SU(5.</a> Nucl. Phys. B. 193, 150-162 (1981).</li><li>The ATLAS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+squarks+and+gluinos+with+the+ATLAS+detector+in+final+states+with+jets+and+missing+transverse+momentum+using+4.7+fb-1+of+&#8730;s+=+7TeV+proton-proton+collisions.">Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 4.7 fb-1 of &#8730;s = 7TeV proton-proton collisions.</a> Phys. Rev. D. , .</li><li>The ATLAS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+squarks+and+gluinos+using+final+states+with+jets+and+missing+transverse+momentum+with+the+ATLAS+detector+in+&#8730;s+=+7TeV+proton-proton+collisions.">Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in &#8730;s = 7TeV proton-proton collisions.</a> Phys. Lett. B. 710, 67-85 (2012).</li><li>The ATLAS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Further+search+for+supersymmetry+at+&#8730;s=7+TeV+in+final+states+with+jets,+missing+transverse+momentum+and+isolated+leptons+with+the+ATLAS+detector.">Further search for supersymmetry at &#8730;s=7 TeV in final states with jets, missing transverse momentum and isolated leptons with the ATLAS detector.</a> Phys. Rev. D. , .</li><li>The CMS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+new+physics+in+the+multijet+and+missing+transverse+momentum+final+state+in+proton-proton+collisions+at+sqrt(s)+=+7+TeV.">Search for new physics in the multijet and missing transverse momentum final state in proton-proton collisions at sqrt(s) = 7 TeV.</a> Phys. Rev. Lett. 109, 171803 (2012).</li><li>The CMS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+supersymmetry+in+pp+collisions+at+&#8730;s=7+TeV+in+events+with+a+single+lepton,+jets,+and+missing+transverse+momentum.">Search for supersymmetry in pp collisions at &#8730;s=7 TeV in events with a single lepton, jets, and missing transverse momentum.</a> J. High Energy Phys. 08, 165 (2011).</li><li>The CMS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+supersymmetry+in+events+with+b-quark+jets+and+missing+transverse+energy+in+pp+collisions+at+7+TeV.">Search for supersymmetry in events with b-quark jets and missing transverse energy in pp collisions at 7 TeV.</a> Phys. Rev. D. 86, 072010 (2012).</li><li>The CMS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=2012+Report+No.:+CMS-PAS-SUS-11-016.">2012 Report No.: CMS-PAS-SUS-11-016.</a> Interpretation of Searches for Supersymmetry. , (2012).</li><li>The CMS Collaboration. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+new+physics+in+events+with+opposite-sign+leptons,+jets,+and+missing+transverse+energy+in+pp+collisions+at+sqrt(s+=+7+TeV.">Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s = 7 TeV.</a> Phys. Lett. B. 718, 815 (2012).</li><li>Alves, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Where+the+Sidewalk+Ends:+Jets+and+Missing+Energy+Search+Strategies+for+the+7+TeV+LHC.">Where the Sidewalk Ends: Jets and Missing Energy Search Strategies for the 7 TeV LHC.</a> JHEP. 1110, 012 (2011).</li><li>Alves, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simplified+Models+for+LHC+New+Physics+Searches.">Simplified Models for LHC New Physics Searches.</a> J. Phys. G.: Nucl. Part. Phys. 39, 105005 (2012).</li><li>Chamseddine, A. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Locally+Supersymmetric+Grand+Unification.">Locally Supersymmetric Grand Unification.</a> Phys. Rev. Lett. 49, 970-974 (1982).</li><li>Barbieri, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gauge+models+with+spontaneously+broken+local+supersymmetry.">Gauge models with spontaneously broken local supersymmetry.</a> Phys. Lett. B. 119, 343-347 .</li><li>Ibanez, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Locally+supersymmetric+SU(5)+grand+unification.">Locally supersymmetric SU(5) grand unification.</a> Phys. Lett. B. 118, 73 (1982).</li><li>Hall, L. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supergravity+as+the+messenger+of+supersymmetry+breaking.">Supergravity as the messenger of supersymmetry breaking.</a> Phys. Rev. D. 27, 2359-2378 (1983).</li><li>Ohta, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grand+Unified+Theories+Based+on+Local+Supersymmetry.">Grand Unified Theories Based on Local Supersymmetry.</a> PTP. 70, 542-549 (1983).</li><li>Chung, D. J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+soft+supersymmetry-breaking+Lagrangian:+theory+and+applications.">The soft supersymmetry-breaking Lagrangian: theory and applications.</a> J. Phys. Rept. 407, 1-203 (2005).</li><li>Alwall, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MadGraph+5:+Going+Beyond.">MadGraph 5: Going Beyond.</a> JHEP. 1106, 128 (2011).</li><li>Pumplin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+Generation+of+Parton+Distributions+with+Uncertainties+from+Global+QCD+Analysis.">New Generation of Parton Distributions with Uncertainties from Global QCD Analysis.</a> JHEP. 0207, 012 (2002).</li><li>Sj&#246;strand, T., Mrenna, S., Skands, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pythia+6.4+Physics+and+Manual.">Pythia 6.4 Physics and Manual.</a> JHEP. 05, 026 (2006).</li><li>. PhysicsResultsSUS &lt; CMSPublic &lt; TWiki [Internet] Available from: <a target="_blank" href="https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSUS">https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSUS</a></li><li>. SupersymmetryPublicResults &lt; AtlasPublic &lt; TWiki [Internet] Available from: <a target="_blank" href="https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults">https://twiki.cern.ch/twiki/bin/view/AtlasPublic/SupersymmetryPublicResults</a> (2013)</li><li>Collaboration, D. 0. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+Squarks+and+Gluinos+in+pp&#772;+collisions+at+&#8730;s=1.8TeV.">Search for Squarks and Gluinos in pp&#772; collisions at &#8730;s=1.8TeV.</a> Phys. Rev. Lett. 75, 618-623 (1995).</li><li>Collaboration, C. D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+Gluinos+and+Scalar+Quarks+in+pp&#772;+collisions+at+&#8730;s=1.8TeV+using+the+Missing+Energy+plus+Multijets+Signature.">Search for Gluinos and Scalar Quarks in pp&#772; collisions at &#8730;s=1.8TeV using the Missing Energy plus Multijets Signature.</a> Phys. Rev. Lett. 88, 041801 (2002).</li><li>Collaboration, C. D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inclusive+Search+for+Squark+and+Gluino+Production+in+pp&#772;+Collisions+at&#8730;s=1.96TeV.">Inclusive Search for Squark and Gluino Production in pp&#772; Collisions at&#8730;s=1.96TeV.</a> Phys. Rev. Lett. 102, 121801 (2009).</li><li>Collaboration, D. 0. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+squarks+and+gluinos+in+events+with+jets+and+missing+transverse+energy+using+2.1fb-1+of+pp&#772;+collision+data+at+&#8730;s=1.96TeV.">Search for squarks and gluinos in events with jets and missing transverse energy using 2.1fb-1 of pp&#772; collision data at &#8730;s=1.96TeV.</a> Phys. Lett. B. 660, 449-457 (2008).</li><li>Collaboration, D. E. L. P. H. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Searches+for+supersymmetric+particles+in+e+e-collisions+up+to+208+GeV+and+interpretation+of+the+results+within+the+MSSM.">Searches for supersymmetric particles in e+e-collisions up to 208 GeV and interpretation of the results within the MSSM.</a> Eur. Phys. J. C. 31, 421-479 (2003).</li><li>Collaboration, L. 3. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+Scalar+Leptons+and+Scalar+Quarks+at+LEP.">Search for Scalar Leptons and Scalar Quarks at LEP.</a> Phys. Lett. B. 580, 37-49 (2004).</li><li>Collaboration, A. T. L. A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Search+for+squarks+and+gluinos+using+final+states+with+jets+and+missing+transverse+momentum+with+the+ATLAS+detector+in+&#8730;s=7TeV+proton-proton+collisions.">Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in &#8730;s=7TeV proton-proton collisions.</a> Phys. Lett. B. 701, 186-203 (2011).</li></ol>

The application of simplified model limits to produce an exclusion contour in a complete new physics model has been demonstrated. Despite the apparent complexity of MSUGRA parameter space points, the kinematics can be well-reproduced by a combination of only a small number of simplified models. The kinematic agreement is further improved when looking within a particular signal region, since the searches thus far conducted at the LHC tend to favor simplified model-like event topologies with a (relatively) small number of ...

One of the most promising extensions of the Standard Model, supersymmetry (SUSY)1-14, is the central focus of many searches by the LHC experiments at CERN. The data collected in 2011 are already sufficient to push the limits of new physics beyond those of any previous collider15-22. As new data arrive and the exclusions are pushed still farther, it will be increasingly important to clearly communicate to the physics community what regions of the extensive supersymmetric parameter space have been excluded. Current limits are typically set on constrained two-dimensional planes, which frequently do not represent the diverse available SUSY parameter space and are difficult to understand as limits on physical masses or branching fractions. A large set of simplified models23, 24 have been proposed for aiding in the understanding of these limits, and both ATLAS and CMS have provided exclusion results for several of these models15-20.
This paper demonstrates the application of these simplified model exclusions to a full new physics model using the example of the minimal supergravity (MSUGRA, also known as the CMSSM)25-30. This model is chosen in order to compare the limits set using simplified models to those published independently by the experiments. The procedure is sufficiently general to be extendable to any new physics model (NPM). As this represents the first attempt to &#34;close the loop&#34; and set limits on SUSY using simplified models, a number of assumptions about the applicability of limits on particular simplified models are explored, resulting in recipes for setting conservative and aggressive limits on theories that have not been examined by the LHC experiments.
For setting a limit in a NPM, three separate operations are required. First, the NPM must be deconstructed into its constituent pieces, separating the various production modes and decay modes for all new particles in the model. Second, a set of simplified models must be chosen to recreate the kinematics and relevant event topologies in the NPM. Third, the available limits on these simplified models must be combined in order to produce limits on the NPM. These three procedures are described in the protocol. Some additional approximations are also provided that may expand the applicability of the already-available simplified models to a broader range of event topologies.
A complete NPM typically involves many production modes and many possible subsequent decays. The deconstruction of new physics models into their components and the application of simplified model limits to those components allows the construction of an exclusion limit directly. For any signal region, the most conservative limit can be set using the production fraction P(a,b)&#160;(where a,b represents the simplified model sparticle production mode) of events identical to a simplified model i and the branching fraction for the produced sparticles to decay in the manner described by the simplified model&#8224;, BRa&#8594; i x BRb &#8594; i. The expected number of events in a given signal region from these simple topologies can then be written as
<img alt="Equation 1" fo:src="/files/ftp_upload/50419/50419eq1highres.jpg" src="/files/ftp_upload/50419/50419eq1.jpg" /> 
where the sum is over simplified models, &#963;tot is the total cross section for the NPM point, Lint is the integrated luminosity used in the search, and AEa,b &#8594; i is the acceptance times efficiency for the simplified model events in the signal region being considered. This number can be compared to the expected 95% confidence level upper limit on the number of new physics events to select the optimal search region. The model can then be excluded if N is larger than the observed number of new physics events excluded at the 95% confidence level. Exclusions in nonoverlapping regions may be combined if information about the correlations of their uncertainties is available. If this information is not available, the best signal region or analysis that provides the best expected limit can be used to attempt to exclude the model.
In order to construct concrete limits with this method, the A&#949; for various simplified models must be made available by the LHC experiments. Both CMS and ATLAS have published figures with the A&#949; for several models, and a few of the figures are available in the HepData database31. In order to demonstrate the value of publishing all such tables, we feel it is important to provide concrete limits that are comparable to those already published. Therefore we use (and describe in the protocol as an optional step) a fast detector simulation to emulate the effect of the ATLAS or CMS detector. The A&#949; derived from the Pretty Good Simulation (PGS)32 is compared to that published by ATLAS in a simplified model grid in Figure 1. These results are sufficiently close to one another (within roughly 25%) that, rather than wait for all results to be public, A&#949; results for the remaining grids are derived using PGS and used directly in the remainder of this paper. As the number of publicly available simplified model A&#949; results grows, the need for such approximations should be significantly reduced.
Two conservative assumptions allow the inclusion of a larger number of production and decay modes in the limit. The first is that for associated production the experimental A&#949; is at least as high as the A&#949; for the worse of the two production modes. For inclusive searches, this is generally a good assumption. The minimum expected number of events would then be
<img alt="Equation 2" fo:src="/files/ftp_upload/50419/50419eq2highres.jpg" src="/files/ftp_upload/50419/50419eq2.jpg" /> 
where the first sum runs over all production modes, and only those where a and b are exactly those particles from the simplified model are included in Equation 1. Similarly, the A&#949; for decays with different legs can be assumed to be at least as high as the A&#949; for the worse of the two legs. That is,
<img alt="Equation 3" fo:src="/files/ftp_upload/50419/50419eq3highres.jpg" src="/files/ftp_upload/50419/50419eq3.jpg" /> 
where diagrams with different decays on either side have now been included.
Two further assumptions would allow the setting of stricter limits. One can assume that the experimental A&#949; for all production modes in the theory is similar to the average A&#949; for the production modes covered by simplified models. In that case, the expected number of events can instead be written as
<img alt="Equation 4" fo:src="/files/ftp_upload/50419/50419eq4highres.jpg" src="/files/ftp_upload/50419/50419eq4.jpg" /> 
where the sums are both over only those production modes covered by simplified models. One might further assume that the A&#949; for all decay modes in the theory is similar to the average A&#949; for those events covered by the simplified model topologies. Then the expected number of events may be written as:
<img alt="Equation 5" fo:src="/files/ftp_upload/50419/50419eq5highres.jpg" src="/files/ftp_upload/50419/50419eq5.jpg" /> 
where again the sums run only over the simplified models. Clearly, the most aggressive MSUGRA limit is provided under this assumption, and a limit set in this manner risks claiming exclusion for regions that would not, in fact, be excluded at the 95% confidence level by a dedicated search. Although the accuracy of these two approximations might be suspect, if the inclusive event kinematics of the simplified models compare favorably to a complete SUSY parameter space point, they may not be unreasonable.
&#8224; Some simplified models now used at the LHC include associated production. While not explicitly discussed here, the equations can be trivially extended to allow for this case.

setting limits on supersymmetry using simplified models

Experimental limits on supersymmetry and similar theories are difficult to set because of the enormous available parameter space and difficult to generalize because of the complexity of single points. Therefore, more phenomenological, simplified models are becoming popular for setting experimental limits, as they have clearer physical interpretations. The use of these simplified model limits to set a real limit on a concrete theory has not, however, been demonstrated. This paper recasts simplified model limits into limits on a specific and complete supersymmetry model, minimal supergravity. Limits obtained under various physical assumptions are comparable to those produced by directed searches. A prescription is provided for calculating conservative and aggressive limits on additional theories. Using acceptance and efficiency tables along with the expected and observed numbers of events in various signal regions, LHC experimental results can be recast in this manner into almost any theoretical framework, including nonsupersymmetric theories with supersymmetry-like signatures.

Having applied the model deconstruction step to a point in the parameter space of MSUGRA, a breakdown of the output can be best visualized by counting up the various production and decay modes for every generated event and plotting the corresponding production rates and branching fractions according to the relative frequencies. The branching fractions for the various production and decay modes for representative MSUGRA points are illustrated in Figures 2 and 3. A large number of similar ...

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Setting Limits on Supersymmetry Using Simplified Models

This paper demonstrates a protocol for recasting experimental simplified model limits into conservative and aggressive limits on an arbitrary new physics model. Publicly available LHC experimental results can be recast in this manner into limits on almost any new physics model with a supersymmetry-like signature.

Experimental limits on supersymmetry and similar theories are difficult to set because of the enormous available parameter space and difficult to ...

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Engineering

Experiments on Ultrasonic Lubrication Using a Piezoelectrically-assisted Tribometer and Optical Profilometer

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at a frequency above the acoustic range (20 kHz). As a solid-state technology, ultrasonic lubrication can be used where conventional lubricants are unfeasible or undesirable. Further, ultrasonic lubrication allows for electrical modulation of the effective friction coefficient between two sliding surfaces. This property enables adaptive systems that modify their frictional state and associated dynamic response as the operating conditions change. Surface wear can also be reduced through ultrasonic lubrication. We developed a protocol to investigate the dependence of friction force reduction and wear reduction on the linear sliding velocity between ultrasonically lubricated surfaces. A pin-on-disc tribometer was built which differs from commercial units in that a piezoelectric stack is used to vibrate the pin at 22 kHz normal to the rotating disc surface. Friction and wear metrics including effective friction force, volume loss, and surface roughness are measured without and with ultrasonic vibrations at a constant pressure of 1 to 4 MPa and three different sliding velocities: 20.3, 40.6, and 87 mm/sec. An optical profilometer is utilized to characterize the wear surfaces. The effective friction force is reduced by 62% at 20.3 mm/sec. Consistently with existing theories for ultrasonic lubrication, the percent reduction in friction force diminishes with increasing speed, down to 29% friction force reduction at 87 mm/sec. Wear reduction remains essentially constant (49%) at the three speeds considered.

We present a protocol for using a piezoelectrically-assisted tribometer and optical profilometer to investigate the dependence of ultrasonic wear and friction reduction on linear velocity, contact pressure, and surface properties.

Friction and wear are detrimental to engineered systems. Ultrasonic lubrication is achieved when the interface between two sliding surfaces is vibrated at ...

Fabrication of 1-D Photonic Crystal Cavity on a Nanofiber Using Femtosecond Laser-induced Ablation

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using femtosecond laser-induced ablation. We show that thousands of periodic nano-craters are fabricated on an optical nanofiber by irradiating with just a single femtosecond laser pulse. For a typical sample, periodic nano-craters with a period of 350 nm and with diameter gradually varying from 50 - 250 nm over a length of 1 mm are fabricated on a nanofiber with diameter around 450 - 550 nm. A key aspect of such a nanofabrication is that the nanofiber itself acts as a cylindrical lens and focuses the femtosecond laser beam on its shadow surface. Moreover, the single-shot fabrication makes it immune to mechanical instabilities and other fabrication imperfections. Such periodic nano-craters on nanofiber, act as a 1-D PhC and enable strong and broadband reflection while maintaining the high transmission out of the stopband. We also present a method to control the profile of the nano-crater array to fabricate apodized and defect-induced PhC cavities on the nanofiber. The strong confinement of the field, both transverse and longitudinal, in the nanofiber-based PhC cavities and the efficient integration to the fiber networks, may open new possibilities for nanophotonic applications and quantum information science.

We present a protocol for fabricating 1-D photonic crystal cavities on subwavelength diameter silica fibers (optical nanofibers) using femtosecond laser-induced ablation.

We present a protocol for fabricating 1-D Photonic Crystal (PhC) cavities on subwavelength-diameter tapered optical fibers, optical nanofibers, using ...

3D Printing of Biomolecular Models for Research and Pedagogy

The construction of physical three-dimensional (3D) models of biomolecules can uniquely contribute to the study of the structure-function relationship. 3D structures are most often perceived using the two-dimensional and exclusively visual medium of the computer screen. Converting digital 3D molecular data into real objects enables information to be perceived through an expanded range of human senses, including direct stereoscopic vision, touch, and interaction. Such tangible models facilitate new insights, enable hypothesis testing, and serve as psychological or sensory anchors for conceptual information about the functions of biomolecules. Recent advances in consumer 3D printing technology enable, for the first time, the cost-effective fabrication of high-quality and scientifically accurate models of biomolecules in a variety of molecular representations. However, the optimization of the virtual model and its printing parameters is difficult and time consuming without detailed guidance. Here, we provide a guide on the digital design and physical fabrication of biomolecule models for research and pedagogy using open source or low-cost software and low-cost 3D printers that use fused filament fabrication technology.

Physical models of biomolecules can facilitate an understanding of their structure-function for the researcher, aid in communication between researchers, and serve as an educational tool in pedagogical endeavors. Here, we provide detailed guidance for the 3D printing of accurate models of biomolecules using fused filament fabrication desktop 3D printers.

The construction of physical three-dimensional (3D) models of biomolecules can uniquely contribute to the study of the structure-function relationship. 3D ...

Surgical Techniques for Catheter Placement and 5/6 Nephrectomy in Murine Models of Peritoneal Dialysis

Peritoneal dialysis (PD) is a renal replacement therapy consistent on the administration and posterior recovery of a hyperosmotic fluid in the peritoneal cavity to drain water and toxic metabolites that functionally-insufficient kidneys are not able to eliminate. Unfortunately, this procedure deteriorates the peritoneum. Tissue damage triggers the onset of inflammation to heal the injury. If the injury persists and inflammation becomes chronic, it may lead to fibrosis, which is a common occurrence in many diseases. In PD, chronic inflammation and fibrosis, along with other specific processes related to these ones, lead to ultrafiltration capacity deterioration, which means the failure and subsequent cessation of the technique. Working with human samples provides information about this deterioration but presents technical and ethical limitations to obtain biopsies. Animal models are essential to study this deterioration since they overcome these shortcomings.
A chronic mouse infusion model was developed in 2008, which benefits from the wide range of genetically modified mice, opening up the possibility of studying the mechanisms involved. This model employs a customized device designed for mice, consisting of a catheter attached to an access port that is placed subcutaneously at the back of the animal. This procedure avoids continuous puncture of the peritoneum during long-term experiments, reducing infections and inflammation due to injections. Thanks to this model, peritoneal damage induced by chronic PD fluid exposure has been characterized and modulated. This technique allows the infusion of large volumes of fluids and could be used for the study of other diseases in which inoculation of drugs or other substances over extended periods of time is necessary.
This article shows the method for the surgical placement of the catheter in mice. Moreover, it explains the procedure for a 5/6 nephrectomy to mimic the state of renal insufficiency present in PD patients.

This article shows the method for the surgical placement in mice of an intraperitoneal catheter attached to an access port that is positioned at the back of the animal. Moreover, it explains the procedure for a 5/6 nephrectomy to resemble the uremic state of PD patients.

Peritoneal dialysis (PD) is a renal replacement therapy consistent on the administration and posterior recovery of a hyperosmotic fluid in the peritoneal ...

Fabrication of Magnetic Nanostructures on Silicon Nitride Membranes for Magnetic Vortex Studies Using Transmission Microscopy Techniques

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared on transparent membranes which are very fragile and difficult to manipulate. We present processes for the fabrication of samples with magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for Lorentz transmission electron microscopy and magnetic transmission x-ray microscopy studies. The samples are prepared on silicon nitride membranes and the fabrication consists of a spin coating, UV and electron-beam lithography, the chemical development of the resist, and the evaporation of the magnetic material followed by a lift-off process forming the final magnetic structures. The samples for the Lorentz transmission electron microscopy consist of magnetic nanodiscs prepared in a single lithography step. The samples for the magnetic x-ray transmission microscopy are used for time-resolved magnetization dynamic experiments, and magnetic nanodiscs are placed on a waveguide which is used for the generation of repeatable magnetic field pulses by passing an electric current through the waveguide. The waveguide is created in an extra lithography step.

A protocol for the fabrication of magnetic micro- and nanostructures with spin configurations forming magnetic vortices suitable for transmission electron microscopy (TEM) and magnetic transmission x-ray microscopy (MTXM) studies is presented.

Electron and x-ray magnetic microscopies allow for high-resolution magnetic imaging down to tens of nanometers. However, the samples need to be prepared ...

Automated Deployment of an Internet Protocol Telephony Service on Unmanned Aerial Vehicles Using Network Functions Virtualization

The Network Function Virtualization (NFV) paradigm is one of the key enabling technologies in the development of the 5th generation of mobile networks. This technology aims to lessen the dependence on hardware in the provision of network functions and services by using virtualization techniques that allow the softwarization of those functionalities over an abstraction layer. In this context, there is increasing interest in exploring the potential of unmanned aerial vehicles (UAVs) to offer a flexible platform capable of enabling cost-effective NFV operations over delimited geographic areas.
To demonstrate the practical feasibility of utilizing NFV technologies in UAV platforms, a protocol is presented to set up a functional NFV environment based on open source technologies, in which a set of small UAVs supply the computational resources that support the deployment of moderately complex network services. Then, the protocol details the different steps needed to support the automated deployment of an internet protocol (IP) telephony service over a network of interconnected UAVs, leveraging the capacities of the configured NFV environment. Experimentation results demonstrate the proper operation of the service after its deployment. Although the protocol focuses on a specific type of network service (i.e., IP telephony), the described steps may serve as a general guide to deploy other type of network services. On the other hand, the protocol description considers concrete equipment and software to set up the NFV environment (e.g., specific single board computers and open source software). The utilization of other hardware and software platforms may be feasible, although the specific configuration aspect of the NFV environment and the service deployment may present variations with respect to those described in the protocol.

The objective of the described protocol is twofold: to configure a network functions virtualization environment using unmanned aerial vehicles as computational entities providing the underlying structure to execute virtualized network functions and to use this environment to support the automated deployment of a functional internet protocol telephony service over the aerial vehicles.

The Network Function Virtualization (NFV) paradigm is one of the key enabling technologies in the development of the 5th generation of mobile networks. ...

Study of a Dot-patterning Process on Flexible Materials using Impact Print-Type Hot Embossing Technology

Here we present our study on an impact print-type hot embossing process which can create dot patterns with various designs, widths, and depths in real time on polymer film. In addition, we implemented a control system for the on-off motion and position of the impact header to engrave different dot patterns. We performed dot patterning on various polymer films, such as polyester (PET) film, polymethyl methacrylate (PMMA) film, and polyvinyl chloride (PVC) film. The dot patterns were measured using a confocal microscope, and we confirmed that the impact print-type hot embossing process produces fewer errors during the dot patterning process. As a result, the impact print-type hot embossing process is found to be suitable for engraving dot patterns on different types of polymer films. In addition, unlike the conventional hot embossing process, this process does not use an embossing stamp. Therefore, the process is simple and can create dot patterns in real time, presenting unique advantages for mass production and small-quantity batch production.

Impact print-type hot embossing technology uses an impact header to engrave dot patterns on flexible materials in real time. This technology has a control system for controlling the on-off motion and position of the impact header to create dot patterns with various widths and depths on different polymer films.

Here we present our study on an impact print-type hot embossing process which can create dot patterns with various designs, widths, and depths in real ...

Fabrication of Surface Acoustic Wave Devices on Lithium Niobate

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order surface acoustic wave (SAW) devices generate enormous accelerations on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid handling at the microscale&#8212;and even at the nanoscale. In this paper we explicitly demonstrate two major fabrication methods of SAW devices on lithium niobate: the details of lift-off and wet etching techniques are described step-by-step. Representative results for the electrode pattern deposited on the substrate as well as the performance of SAW generated on the surface are displayed in detail. Fabrication tricks and troubleshooting are covered as well. This procedure offers a practical protocol for high frequency SAW device fabrication and integration for future microfluidics applications.

Two fabrication techniques, lift-off and wet etching, are described in producing interdigital electrode transducers upon a piezoelectric substrate, lithium niobate, widely used to generate surface acoustic waves now finding broad utility in micro to nanoscale fluidics. The as-produced electrodes are shown to efficiently induce megahertz order Rayleigh surface acoustic waves.&#160;

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order ...

Manufacturing, Control, and Performance Evaluation of a Gecko-Inspired Soft Robot

This protocol presents a method for manufacturing, control, and evaluation of the performance of a soft robot that can climb inclined flat surfaces with slopes of up to 84&#176;. The manufacturing method is valid for the fast pneunet bending actuators in general and might, therefore, be interesting for newcomers to the field of actuator manufacturing. The control of the robot is achieved by means of a pneumatic control box that can provide arbitrary pressures and can be built by only using purchased components, a laser cutter, and a soldering iron. For the walking performance of the robot, the pressure-angle calibration plays a crucial role. Therefore, a semi-automated method for the pressure-angle calibration is presented. At high inclines (&#62; 70&#176;), the robot can no longer reliably fix itself to the walking plane. Therefore, the gait pattern is modified to ensure that the feet can be fixed on the walking plane.

This protocol provides a detailed list of steps to be performed for the manufacturing, control and evaluation of the climbing performance of a gecko-inspired soft robot.

This protocol presents a method for manufacturing, control, and evaluation of the performance of a soft robot that can climb inclined flat surfaces with ...

Micro-Embossed Fabrication of Nanocellulose Paper-Based Analytical Devices  

Microembossing: A Convenient Process for Fabricating Microchannels on Nanocellulose Paper-Based Microfluidics

Nanopaper, derived from nanofibrillated cellulose, has generated considerable interest as a promising material for microfluidic applications. Its appeal lies in a range of excellent&#160;qualities, including an exceptionally smooth surface, outstanding optical transparency, a uniform nanofiber matrix with nanoscale porosity, and customizable chemical properties. Despite the rapid growth of nanopaper-based microfluidics, the current techniques used to create microchannels on nanopaper, such as 3D printing, spray coating, or manual cutting and assembly, which are crucial for practical applications, still possess certain limitations, notably susceptibility to contamination. Furthermore, these methods are restricted to the production of millimeter-sized channels. This study introduces a straightforward process that utilizes convenient plastic micro-molds for simple microembossing operations to fabricate microchannels on nanopaper, achieving a minimum width of 200 &#181;m. The developed microchannel outperforms existing approaches, achieving a fourfold improvement, and can be fabricated within 45 min. Furthermore, fabrication parameters have been optimized, and a convenient quick-reference table is provided for application developers. The proof-of-concept for a laminar mixer, droplet generator, and functional nanopaper-based analytical devices (NanoPADs) designed for Rhodamine B sensing using surface-enhanced Raman spectroscopy was demonstrated. Notably, the NanoPADs exhibited exceptional performance with improved limits of detection. These outstanding results can be attributed to the superior optical properties of nanopaper and the recently developed accurate microembossing method, enabling the integration and fine-tuning of the NanoPADs.

Author Spotlight: Revolutionizing Microfluidics Through Microchannel Fabrication on Nanopaper 

This protocol describes a straightforward process that utilizes convenient plastic micro-molds for simple microembossing operations to fabricate microchannels on nanofibrillated cellulose paper, achieving a minimum width of 200 &#181;m.

Nanopaper, derived from nanofibrillated cellulose, has generated considerable interest as a promising material for microfluidic applications. Its appeal ...