Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions

Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions

The results of search for superparticles in final states with jets, muons and missing transverse energy are presented. The study is based on a data obtained in proton-proton collisions at √s = 7 TeV. They correspond to 4.36 fb⁻¹ of integrated luminosity collected with the CMS detector in 2011. mSUGR...

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Datum:2015
Hauptverfasser: Lukyanenko, S.T., Obikhod, T.V.
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Veröffentlicht: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2015
Schriftenreihe:Вопросы атомной науки и техники
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Ядерная физика и элементарные частицы
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spelling irk-123456789-1121252017-01-18T03:03:19Z Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions Lukyanenko, S.T. Obikhod, T.V. Ядерная физика и элементарные частицы The results of search for superparticles in final states with jets, muons and missing transverse energy are presented. The study is based on a data obtained in proton-proton collisions at √s = 7 TeV. They correspond to 4.36 fb⁻¹ of integrated luminosity collected with the CMS detector in 2011. mSUGRA/MSSM model built in generator PYTHIA6 was used for SUSY signal modeling. Two selection criteria for searching SUSY- manifesting were used. Background from Standard Model processes was estimated using the MADGRAPH and POWHEG generators. It is shown that with confidence level 95% the data are found to be in agreement with Standard Model expectations and new physics effects are not observed in ranges ETmiss >200 GeV and Meffinc >600 GeV. Наведено результати пошуку суперчастинок із мюонами, струменями і втраченою поперечною енергією в кінцевому стані. Вивчення ґрунтується на даних, отриманих при протон-протонних зіткненнях при енергії √s = 7 ТеВ, що відповідають інтегрованій світимості 4.36 fb⁻¹, накопиченій CMS детектором в 2011 році. Для моделювання SUSY сигналу використовувалась модель mSUGRA/MSSM, вбудована в пакет PYTHIA6. Розглядалось два критерії відбору для пошуку SUSY подій. За допомогою генераторів MADGRAPH и POWHEG були оцінені фони, обумовлені процессами Стандартної Моделі. Показано, що з рівнем довіри 95% отримані результати знаходяться у відповідності із передбаченнями Стандартної Моделі і в межах ETmiss >200 ГеВ і Meffinc >600 ГеВ ефекти нової фізики не спостерігаються. Представлены результаты поиска суперчастиц с мюонами, струями и потерянной поперечной энергией в конечном состоянии. Изучение основано на данных, полученных в протон-протонных столкновениях при энергии √=7 ТэВ и соответствующих интегральной светимости 4.36 fb⁻¹ , накопленной CMS детектором в 2011 году. Для моделирования SUSY сигнала использовалась модель mSUGRA/MSSM, встроенная в пакет PYTHIA6. Рассматривалось два критерия отбора для поиска SUSY событий. С помощью генераторов MADGRAPH и POWHEG были оценены фоны, обусловленные процессами Стандартной Модели. Показано, что с уровнем доверия 95% полученные результаты находятся в согласии с предсказаниями Стандартной Модели и в пределах ETmiss >200 ГэВ и Meffinc >600 ГэВ эффекты новой физики не наблюдаются. 2015 Article Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions / S.T. Lukyanenko, T.V. Obikhod // Вопросы атомной науки и техники. — 2015. — № 3. — С. 7-12. — Бібліогр.: 18 назв. — англ. 1562-6016 PACS: 11.25.-w, 12.60.Jv, 02.10.Ws http://dspace.nbuv.gov.ua/handle/123456789/112125 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Ядерная физика и элементарные частицы
Ядерная физика и элементарные частицы
spellingShingle Ядерная физика и элементарные частицы
Ядерная физика и элементарные частицы
Lukyanenko, S.T.
Obikhod, T.V.
Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions
Вопросы атомной науки и техники
description The results of search for superparticles in final states with jets, muons and missing transverse energy are presented. The study is based on a data obtained in proton-proton collisions at √s = 7 TeV. They correspond to 4.36 fb⁻¹ of integrated luminosity collected with the CMS detector in 2011. mSUGRA/MSSM model built in generator PYTHIA6 was used for SUSY signal modeling. Two selection criteria for searching SUSY- manifesting were used. Background from Standard Model processes was estimated using the MADGRAPH and POWHEG generators. It is shown that with confidence level 95% the data are found to be in agreement with Standard Model expectations and new physics effects are not observed in ranges ETmiss >200 GeV and Meffinc >600 GeV.
format Article
author Lukyanenko, S.T.
Obikhod, T.V.
author_facet Lukyanenko, S.T.
Obikhod, T.V.
author_sort Lukyanenko, S.T.
title Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions
title_short Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions
title_full Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions
title_fullStr Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions
title_full_unstemmed Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions
title_sort search for supersymmetry using final states with muons, jets, and missing transverse momentum with the cms detector in √ s = 7 tev pp collisions
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
publishDate 2015
topic_facet Ядерная физика и элементарные частицы
url http://dspace.nbuv.gov.ua/handle/123456789/112125
citation_txt Search for supersymmetry using final states with muons, jets, and missing transverse momentum with the CMS detector in √ s = 7 TeV pp collisions / S.T. Lukyanenko, T.V. Obikhod // Вопросы атомной науки и техники. — 2015. — № 3. — С. 7-12. — Бібліогр.: 18 назв. — англ.
series Вопросы атомной науки и техники
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first_indexed 2025-07-08T03:25:58Z
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fulltext SEARCH FOR SUPERSYMMETRY USING FINAL STATES WITH MUONS, JETS, AND MISSING TRANSVERSE MOMENTUM WITH THE CMS DETECTOR IN √ s = 7TeV pp COLLISIONS S.T.Lukyanenko1, T.V.Obikhod 2∗ 1National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine; 2Institute for Nuclear Research National Academy of Sciences of Ukraine, 03068, Kiev, Ukraine (Received April 6, 2015) The results of search for superparticles in final states with jets, muons and missing transverse energy are presented. The study is based on a data obtained in proton-proton collisions at √ s = 7 TeV. They correspond to 4.36 fb−1 of integrated luminosity collected with the CMS detector in 2011. mSUGRA/MSSM model built in generator PYTHIA6 was used for SUSY signal modeling. Two selection criteria for searching SUSY- manifesting were used. Background from Standard Model processes was estimated using the MADGRAPH and POWHEG generators. It is shown that with confidence level 95% the data are found to be in agreement with Standard Model expectations and new physics effects are not observed in ranges Emiss T >200 GeV and Minc eff >600 GeV. PACS: 11.25.-w, 12.60.Jv, 02.10.Ws 1. INTRODUCTION The most powerful particle accelerator Large Hadron Collider (LHC) allows scientists to reproduce the con- ditions after the Big Bang through their recreating by colliding proton beams. The essential parts of the LHC project are four huge detectors (ATLAS, CMS, ALICE, LHCb) and the Worldwide LHC Comput- ing Grid (WLCG). Researchers expect not only to confirm known experiments and theories but also to discover new particles and to test the theories for un- derstanding the origin of the Universe. ATLAS and CMS are two general-purpose detec- tors at the LHC for investigation a wide range of physics in high-energy collisions including the search for the properties of the discovered Higgs boson, su- persymmetric paricles and the evidence for dark mat- ter in the Universe. Through many experiments, the Standard Model has become established as a well-tested physics the- ory. The theory incorporates only three out of the four fundamental forces, omitting gravity. Last but not least is a particle called the Higgs boson, an essen- tial component of the Standard Model discovered in 2012. Even though the Standard Model is the best description of the subatomic world, it does not ex- plain the complete picture. There are also important issues that it does not answer, such as the nature of the dark matter, or the matter/antimatter problem, the three generations of quarks and leptons with such a different mass scale, etc. So, the Standard Model is perhaps only a part of a bigger picture that includes new physics. New information from experiments at the LHC will possibly help us to find more of these missing pieces. Currently there are experimental data that may turn out to be a signal of new physics be- yond Standard Model: • LHCb has now analysed the ratio of the number of decays containing muons, to those containing elec- trons from proton-proton collisions on the LHC and found that B mesons decay to muons about 25% less than they decay to electrons [1]; • the Higgs boson production in association with a top-quark pair represents the excess, which is equiv- alent to a 2-standard-deviation above the SM [2]. Basing on all of the above, it is clear that currently a priority activity for the largest collaborations at CERN is a search for new hypothetical particles and possible effects indicating deviations from the Stan- dard Model. The aim of our experimental work is the search for effects of new physics within the supersymmetry theory (SUSY), which is one of the best studied the- ories beyond the SM. Such a symmetry predicts the existence of supersymmetric particles, abbreviated as sparticles, such as sleptons, squarks, neutralinos, gluinos and charginos . Due to the supersymmetry breaking, the sparticles are much heavier than their ordinary counterparts [3]. The Minimal Supersymmetric Standard Model (MSSM) is one of the best candidates for physics be- yond the Standard Model . It is characterized by five free parameters of mSUGRA model [4]: m0 – the uni- ∗Corresponding author E-mail address: obikhod@kinr.kiev.ua ISSN 1562-6016. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2015, N3(97). Series: Nuclear Physics Investigations (64), p.7-12. 7 versal mass of the scalars (sleptons, squarks, Higgs bosons) at the Grand Unification scale, m1/2 – the universal mass of the gauginos and higgsinos at the Grand Unification scale, A0 – the universal trilinear coupling, tanβ – the ratio of the vacuum expectation values of the two Higgs doublets, sign(µ) – the sign of the higgsino mass parameter. The paper presents the results of searching for SUSY signal, described by such model with certain values of parameters. First searches for the production of SUSY par- ticles at the Large Hadron Collider (LHC) corre- sponded to a total integrated luminosity of 35 pb−1 with jets and significant missing transverse energy [5, 6, 7] in final states. More recent publications [8] are based on a 20.3 fb−1 dataset of √ s = 8 TeV proton-proton collisions in final states with jets and missing transverse momentum. SUSY particles, the squarks q̃ and gluinos g̃ are expected to be produced via the strong interaction at the TeV energy scale. Their decays via cas- cades ending with the lightest supersymmetric par- ticle (LSP) produce experimental signatures leading to final states containing multi-jets, charged leptons and large missing transverse momentum (undetected neutralino and possibly leptons). Taking into account the large number of possi- ble final states after the decay of a SUSY particle, we have tried to summarize their contributions with an appropriate choice of kinematical constraints for registration of possible signal. The article does not suggest an original approach in such studies and does not propose a new method of data analysis. It is not contradict earlier researches (see above) and, actually, presents the tests of our algorithms. These algorithms can be used for processing and analysis of future CMS data. 2. DATA AND EVENT SELECTION SUSY particles, the squarks (q̃) and gluinos (g̃) are mainly produced, with large probability, via direct production of g̃g̃, q̃g̃ or q̃q̃ pairs. Squarks typically generate at least one jet in their decays, while gluinos typically generate at least two jets. Processes with q̃q̃, q̃g̃ and g̃g̃ in intermediate states therefore lead to events containing at least two, three or four jets, re- spectively. Using a data obtained in pp collisions at√ s = 7 TeV, we perform the search for massive SUSY particles that decay to the muons, jets and neutrali- nos. Two of many possible processes of superparticle decays are presented in Fig.1. We used the data sample collected during 2011 by the Compact Muon Solenoid (CMS) - a multipurpose detector described in detail in [9]. Searches in final states with many jets, leptons, and large missing transverse energy in final states are sensitive to a wide range of new models, includ- ing SUSY. Such searches were performed in [10]. a b Fig.1. Processes of superparticle decay after pp collisions: a) decay of gluinos; b) decay of squarks We begin the search for the superparticle sig- natures with four hard jets, two high-energetic isolated muons and large Emiss T . The analysis uses a muon sample of CMS experimental data /DoubleMu/Run2011∗PromptReco∗/AOD contain- ing in each event at least two muons with transverse momentum pµT above 200 MeV in the pseudorapidity range |ηµ| < 2.7. The pseudorapidity η is defined as η = − ln[tan(θ/2)], where θ is the polar angle with respect to the beam axis. Using the methods of the PAT (Physical Analysis Toolkit) package [11], implemented in the CMS soft- ware package (CMSSW) [12], and WLCG infrastruc- ture [13], we got a sample of preselected events. This sample meets the criteria of high-level muon trigger HLT Mu13 Mu8 (at least two muons with pµT > 13 and pµT > 8 GeV) and corresponds to integrated lumi- nosity Lint = 4.36 fb−1. It was recorded on the disk storage of KIPT CMS Tier-2 Center (T2 UA KIPT ) and used for the final analysis. Events are required to have at least two opposite sign isolated ”signal” muons with pµT above 10 GeV, |ηµ| < 2.4, and the leading muon must have pµT > 20 GeV; at least four hadron ”signal” jets with a transverse momentum pjetT > 30 GeV, |ηjet| < 2.5; missing transverse mo- mentum Emiss T must exeed 100 GeV and must sat- isfy restriction Emiss T /Meff > 0.2, where the effective mass Meff is the scalar sum of pjetT of four leading jets and Emiss T is absolute value of the vector sum of the transverse momentums of the all reconstructed phys- ical objects. The last criterion allows us to suppress the background caused by incorrectly reconstructed hadronic jets more efficiently. Two event distributions will be analyzed using the main observables Emiss T and inclusive effective mass Minc eff . Quantity Minc eff is defined in terms of the scalar sum of pjetT of all ”signal” jets, the pµT of all ”signal” 8 muons and missing transverse energy, Emiss T : M inc eff = Nlep∑ i=1 pT,i µ + Njet∑ j=1 pjetT,j + Emiss T . These selection criteria choose two high-energetic muons, four hard jets and two LSPs mainly in pro- cesses pp → q̃q̃ + X → qq + ZZ + χ̃0 1χ̃ 0 1 + X and pp → q̃q̃∗ + X → q ′ q + WZ + χ̃0 1χ̃ 0 1 + X, where q̃ is squark, q̃∗ - antisquark, q - antiquark. The main criterion for manifestation of SUSY particles is a cer- tain excess of events in the distribution of Minc eff or Emiss T compared to the Standard Model predictions. The excess, if it exists, must occur at sufficiently large values Minc eff and Emiss T and is directly connected with the large masses of the superpartners. The signal es- timation is based on Monte Carlo samples generated by PYTHIA6 [14] and reconstructed with taking into account the CMS detector response. The SUSY sig- nal in the mSUGRA/MSSM model is defined for m0 = 500 GeV, m1/2 = 300 GeV, A0 = - 300 GeV, tan β = 10, sign(µ)> 0. Contamination of the signal region due to back- ground from the following Standard Model processes is estimated: • Di-boson (WW, WZ, ZZ boson pairs) + jets pro- duction events generated using the MADGRAPH generator [15]; • tt + jets and tW + jets production estimated using the MADGRAPH and POWHEG [16] correspond- ingly; • Z+jets production generated using the MAD- GRAPH generator. POWHEG background simulation results include the real and virtual next-to-leading-order (NLO) correc- tions. The MADGRAPH gives an opportunity to consider in tree approximation the processes leading to 5 jets. All Monte-Carlo results for the distribution of events presented in the paper are rescaled taking into account the static factor K = σtot theor/σ tot gen (σtot gen - cross section calculated by the events gener- ator and σtot theor - cross section including higher-order corrections to leading process), and an integrated luminosity of 4.36 fb−1. 3. RESULTS Application of the above criteria for the selection of events leads to poor statistics for the signal (∼ 3 events over the entire range of Minc eff or Emiss T ). Therefore, a natural step is to loosen the kine- matic constraints on the selection of SUSY events. We add a signature containing the final states with one muon, which corresponds, for example, to pro- cess pp → q̃q̃ + X → q ′ q ′ + WW + χ̃0 1χ̃ 0 1 + X and further reduce the threshold for pT of leading muon. As a result, we have the following set of constraints: at least one isolated signal muon pµT > 10 GeV, |ηµ| < 2.4; at least four hadron ”signal” jets pjetT > 30 GeV, |ηjet| < 2.5; Emiss T > 100 GeV; Emiss T /Meff > 0.2.  (1) The event distributions over Emiss T and Minc eff for CMS experimental data are shown in Fig.2. Expec- tation for the mSUGRA/MSSM model and the con- tribution of the main background processes are also shown. , GeV miss TE 0 200 400 600 800 1000 E v e n ts / 1 0 0 G e V 1 10 210 SUSY results CMS experiment -1 =4.36 fb int =7 TeV, Ls CMS data MC simulation: --- - MSSM signal: =300 GeV, 1/2 =500 GeV, m0m >0m=10,b=-300 GeV, tan0A Background contributions: +jets 0 Z + Wt+ - tW +jetstt +jets - W + W +jets – W 0 Z +jets 0 Z 0 Z , GeV inc effM 0 200 400 600 800 1000 1200 1400 1600 1800 2000 E v e n ts / 2 0 0 G e V 1 10 210 SUSY results CMS experiment -1 =4.36 fb int =7 TeV, Ls CMS data MC simulation: --- - MSSM signal: =300 GeV, 1/2 =500 GeV, m0m >0m=10,b=-300 GeV, tan0A Background contributions: +jets 0 Z + Wt+ - tW +jetstt +jets - W + W +jets – W 0 Z +jets 0 Z 0 Z Fig.2. The event distributions over Emiss T and Minc eff satisfying selection criteria (1) are shown (only statistical errors are shown) 9 Experimental data are qualitatively in agreement with the Standard Model expectations. Quantitative contributions of separate sources of the background for various ranges in Emiss T and Minc eff are presented in Table 1. Contribution of the expected signal as well as the yield of real data is shown too. All quan- tities presented in this table are obtained with taking into account only statistical errors. Then, for trig- ger HLT Mu13 Mu8 that is used here, it can be assumed that the contribution of background W + jets will be very small. Table 1. Expected (Total+Signal) and observed (Data) number of events satisfying selection criteria (1) for different ranges in Emiss T and Minc eff ZZ+jets ZW+jets WW+jets tt+jets tW+jets Z+jets Total Signal Data Emiss T >100 GeV 0.3±0.0 0.9±0.1 1.1±0.1 67.2±4.8 3.5±0.5 2.6±1.0 75.5±0.6 20.0±0.5 64±8 Minc eff > 200 GeV Emiss T >200 GeV 0.1 ± 0.0 0.1±0.0 0.2±0.1 5.8±1.4 0.4±0.2 0.7±0.5 7.4±0.1 10.8±0.4 6±2.5 Minc eff > 600 GeV 0.1±0.0 0.2±0.0 0.4±0.1 15.8±2.3 0.9±0.3 0.7±0.5 18.1±0.3 14.5±0.4 13±3.6 Using the Bayesian method [17] the upper limits on signal strength R (the ratio the number of ob- served signal events to the number of expected sig- nal events) has been calculated with the confidence level CL=95%. Quantities presented in Table 2 indi- cate the absence with CL=95% of any effects of new physics described by the selected model (except for case where R< 2.47 ± 0.04). The signal significance is defined from simulated data as S/ √ B, where S is the number of signal events and B is the number of background events. Along with taking into ac- count the statistical errors, for calculating the upper limits we used the systematical errors as well. The maximum systematical errors are considered for sig- nal and background separately (30% - signal, 60% - background). They are taken from studies of article [18]. Table 2. Left to right: signal significance for the various ranges in Emiss T and Minc eff . The third column shows the 95% CL upper limits on the observed signal strength R, calculated with the statistical errors. The last column shows the 95% CL upper limits on the observed signal strength R, taking into account the total uncertainties (see text) S/ √ B R < Rup staterr R< Rup toterr Emiss T >100 GeV, 2.3 R< 0.65 ± 0.01 R< 2.47 ± 0.04 Minc eff > 200 GeV Emiss T >200 GeV 4 R< 0.57 ± 0.01 R< 0.88 ± 0.02 Minc eff > 600 GeV 3.4 R< 0.46 ± 0.01 R< 0.91 ± 0.02 , GeV miss TE 0 200 400 600 800 1000 E v e n ts / 1 0 0 G e V 1 10 210 SUSY results CMS experiment -1 =4.36 fb int =7 TeV, Ls CMS data MC simulation: --- - MSSM signal: =300 GeV, 1/2 =500 GeV, m0m >0m=10,b=-300 GeV, tan0A Background contributions: +jets 0 Z + Wt+ - tW +jetstt +jets - W + W +jets – W 0 Z +jets 0 Z 0 Z , GeV inc effM 0 200 400 600 800 1000 1200 1400 1600 1800 2000 E v e n ts / 2 0 0 G e V 1 10 210 SUSY results CMS experiment -1 =4.36 fb int =7 TeV, Ls CMS data MC simulation: --- - MSSM signal: =300 GeV, 1/2 =500 GeV, m0m >0m=10,b=-300 GeV, tan0A Background contributions: +jets 0 Z + Wt+ - tW +jetstt +jets - W + W +jets – W 0 Z +jets 0 Z 0 Z Fig.3. The event distributions over Emiss T and Minc eff satisfying selection criteria (2) are shown (only statistical errors are shown) Note that we are not bound in our consideration to any particular SUSY process. We are interested in the total contribution of the group of processes, selected by the relevant criteria. Therefore, it makes sense to calculate CL for a group of processes, which, in addition to those already discussed, will include also formation of three hard jets and χ̃0 2 → Zχ̃0 1. The cuts in this case are as follows: 10 at least two isolated opposite-sign ”signal” muons pµT > 10 GeV, |ηµ| < 2.4 including one leading muon with pµT > 20 GeV; at least two hadron ”signal” jets pjetT > 30 GeV, |ηjet| < 2.5; Emiss T > 100 GeV; Emiss T /M ′ eff > 0.2.  (2) HereM ′ eff is the scalar sum of pjetT of two leading jets. The result of their application is shown in Fig.3. Quantitative contributions of separate sources of the background for various ranges in Emiss T and Minc eff are presented in Table 3. Contribution of the ex- pected signal as well as yield of real data is shown too. All quantities presented in this table are ob- tained with taking into account only statistical er- rors. Table 3. Expected (Total + Signal) and observed (Data) number of events satisfying selection criteria (2) for different ranges in Emiss T and Minc eff ZZ+jets ZW+jets WW+jets tt+jets tW+jets Z+jets Total Signal Data Emiss T >100 GeV 1.4±0.0 4.7±0.1 6.4±0.3 116.7±4.7 6.4±0.7 13.2±2.2 148.7±0.3 10.5±0.5 140±11.8 Minc eff > 200 GeV Emiss T >200 GeV 0.3±0.0 0.6±0.1 0.7±0.1 4.5±0.9 0.3±0.2 1.5±0.7 7.9±0.1 6.2±0.4 6±2.5 Minc eff > 600 GeV 0.3±0.0 1.2±0.1 1.6±0.2 9.9±1.4 1.1±0.3 2.9±1.0 16.9±0.1 6.5±0.4 17±4.1 Despite the increase in the number of analyzed SUSY-processes, the increase in the signal did not occur. Furthermore, the signal became smaller com- pared to selection criteria 1. The main reasons for this are, firstly, the smaller number of signal events with two ”good” (satisfying the CMS identification criteria) muons, and secondly, small relative proba- bility of weak boson decay to leptons. At the same time, criteria (2) suppress the background to about the same degree of criteria (1) do. The restriction on the existence of the SUSY signals turn out to be less stringent (see Table 4). Table 4. Left to right: signal significance for the various ranges in Emiss T and Minc eff . The third column shows the 95% CL upper limits on the observed signal strength R, calculated with the statistical errors. The last column shows the 95% CL upper limits on the observed signal strength R, taking into account the total uncertainties (see text) S/ √ B R<Rup staterr R<Rup toterr Emiss T >100 GeV, 0.9 R< 1.94 ± 0.02 R< 10.15 ± 0.25 Minc eff > 200 GeV Emiss T >200 GeV 2.2 R< 0.99 ± 0.02 R< 1.44 ± 0.03 Minc eff > 600 GeV 1.6 R< 1.58 ± 0.01 R< 2.72 ± 0.04 4. CONCLUSIONS We performed a search for superparticles in events with either one or two muons, two or more jets, and large missing transverse energy using 4.36 fb−1 of √ s = 7 TeV CMS data. The event distributions over Minc eff and Emiss T are presented for two sets of se- lection criteria. For different ranges in Emiss T and Minc eff we defined the upper limits on observed signal strength R with confidence level CL=95%. In case of the selection criteria (1), the estimations with the statistical and the maximum systematic error (up to 30% for signal and 60% for background) give the up- per limit values 0.88 and 0.91 for Emiss T >200 GeV and Minc eff >600 GeV, respectively. This confirms with the confidence level 95% the conclusion about the absence of SUSY signal for Emiss T >200 GeV and Minc eff >600 GeV. No excess of events over the ex- pected SM background was observed in experimental CMS data. The proposed method allows us to search for superparticles within different theoretical models, as well as at higher LHC energies. References 1. LHCb collaboration. Rare decays at the LHCb experiment // e-print arXiv:1410.2411 [hep-ex]. 2. The CMS Collaboration. Search for the associ- ated production of the Higgs boson with a top- quark pair // e-print arXiv:1408.1682 [hep-ex] (2014). 3. H.E. Haber. Introductory Low-Energy Super- symmetry// e-print arXiv: hep-ph/9306207, (1993). 4. J.J. Heckman, and C. Vafa. F-theory, GUTs, and the weak scale // e-print arXiv:0809.1098 [hep- th]. 5. ATLAS Collaboration. Search for supersymme- try using final states with one lepton, jets, and missing transverse momentum with the AT- LAS detector in √ s = 7 TeV pp // e-print arXiv:1102.2357v1 [hep-ex] (2011), submitted to Phys. Rev. Lett. 6. ATLAS Collaboration. Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in √ s = 7 TeV proton-proton collisions // e-print arXiv:1102.5290v1 [hep-ex] (2011), submitted to Phys. Lett. 7. CMS Collaboration. Search for Supersymme- try in pp Collisions at 7 TeV in Events with Jets and Missing Transverse Energy // e-print 11 arXiv:1101.1628 [hep-ex] (2011), submitted to Phys. Lett. 8. Marija Marjanovic, for the ATLAS Collabora- tion. Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using 20.3 fb−1 of√ s=8TeV proton-proton collision data // e-print arXiv:1408.5857 [hep-ex]. 9. CMS Collaboration. The CMS experiment at the CERN LHC // JINST 3 (2008) S 08004. 10. ATLAS Collaboration. Search for supersymme- try using final states with one lepton, jets, and missing transverse momentum with the ATLAS detector in √ s = 7TeV pp // e-print arXiv:1102.2357 [hep-ex]. 11. https://twiki.cern.ch/twiki/bin/view/ CMSPublic/WorkBookPAT 12. http://cms-sw.github.io/index.html 13. http://wlcg.web.cern.ch/ 14. T. Sjostrand, S. Mrenna and P. Skands. PYTHIA 6.4 Physics and Manual // JHEP. 2006, 05, p.1-26. 15. Johan Alwall, Pavel Demin, Simon de Visscher, et al. MadGraph/MadEvent v4: The New Web Generation // JHEP 0709:028, 2007, e-print arXiv:0706.2334. 16. Emanuele Re. Single-top Wt-channel pro- duction matched with parton showers using the POWHEG method // Eur.Phys.J. 2011, C71:1547, e-print arXiv:1009.2450. 17. J. Beringer et al. (Particle Data Group) // Phys. Rev. 2012, D8, p. 386-401. 18. CMS Collaboration. Search for new physics in events with opposite-sign leptons, jets, and miss- ing transverse energy in pp collisions at sqrt(s) = 7 TeV // Phys. Lett. 2013, B 718, 815 - 840, e-print arXiv:1206.3949. ÏÎÈÑÊÈ ÑÓÏÅÐÑÈÌÌÅÒÐÈÈ Ñ ÌÞÎÍÀÌÈ, ÑÒÐÓßÌÈ È ÏÎÒÅÐßÍÍÎÉ ÏÎÏÅÐÅ×ÍÎÉ ÝÍÅÐÃÈÅÉ Â ÊÎÍÅ×ÍÎÌ ÑÎÑÒÎßÍÈÈ Ñ ÏÎÌÎÙÜÞ CMS ÄÅÒÅÊÒÎÐÀ ÏÐÈ ÝÍÅÐÃÈÈ √ s = 7Òý  pp - ÑÒÎËÊÍÎÂÅÍÈßÕ Ñ.Ò. Ëóêüÿíåíêî, Ò.Â. Îáèõîä Ïðåäñòàâëåíû ðåçóëüòàòû ïîèñêà ñóïåð÷àñòèö ñ ìþîíàìè, ñòðóÿìè è ïîòåðÿííîé ïîïåðå÷íîé ýíåðãèåé â êîíå÷íîì ñîñòîÿíèè. Èçó÷åíèå îñíîâàíî íà äàííûõ, ïîëó÷åííûõ â ïðîòîí-ïðîòîííûõ ñòîëêíîâåíèÿõ ïðè ýíåðãèè √ s = 7Òý è ñîîòâåòñòâóþùèõ èíòåãðàëüíîé ñâåòèìîñòè 4.36 fb−1, íàêîïëåííîé CMS äåòåêòîðîì â 2011 ãîäó. Äëÿ ìîäåëèðîâàíèÿ SUSY ñèãíàëà èñïîëüçîâàëàñü ìîäåëü mSUGRA/MSSM , âñòðîåííàÿ â ïàêåò PY THIA6. Ðàññìàòðèâàëîñü äâà êðèòåðèÿ îòáîðà äëÿ ïîèñêà SUSY ñîáûòèé. Ñ ïîìîùüþ ãåíåðàòîðîâ MADGRAPH è POWHEG áûëè îöåíåíû ôîíû, îáóñëîâëåííûå ïðîöåññàìè Ñòàíäàðòíîé Ìîäåëè. Ïîêàçàíî, ÷òî ñ óðîâíåì äîâåðèÿ 95% ïîëó÷åííûå ðåçóëüòàòû íàõîäÿòñÿ â ñî- ãëàñèè ñ ïðåäñêàçàíèÿìè Ñòàíäàðòíîé Ìîäåëè è â ïðåäåëàõ Emiss T > 200 èM inc eff > 600 ýôôåêòû íîâîé ôèçèêè íå íàáëþäàþòÿ. ÏÎØÓÊÈ ÑÓÏÅÐÑÈÌÅÒÐI� IÇ ÌÞÎÍÀÌÈ, ÑÒÐÓÌÅÍßÌÈ I ÂÒÐÀ×ÅÍÎÞ ÏÎÏÅÐÅ×ÍÎÞ ÅÍÅÐÃI�Þ Â ÊIÍÖÅÂÎÌÓ ÑÒÀÍI ÇÀ ÄÎÏÎÌÎÃÎÞ CMS ÄÅÒÅÊÒÎÐÀ ÏÐÈ ÅÍÅÐÃI� √ s = 7ÒåÂ Ó pp - ÇIÒÊÍÅÍÍßÕ Ñ.Ò. Ëóê'ÿíåíêî, Ò.Â. Îáiõîä Íàâåäåíî ðåçóëüòàòè ïîøóêó ñóïåð÷àñòèíîê iç ìþîíàìè, ñòðóìåíÿìè i âòðà÷åíîþ ïîïåðå÷íîþ åíåðãi¹þ â êiíöåâîìó ñòàíi. Âèâ÷åííÿ  ðóíòó¹òüñÿ íà äàíèõ, îòðèìàíèõ ïðè ïðîòîí-ïðîòîííèõ çiòêíåííÿõ ïðè åíåðãi¨ √ s = 7Òå , ùî âiäïîâiäàþòü iíòåãðîâàíié ñâiòèìîñòi 4.36 fb−1, íàêîïè÷åíié CMS äåòåêòîðîì ó 2011 ðîöi. Äëÿ ìîäåëþâàííÿ SUSY ñèãíàëó âèêîðèñòîâóâàëàñü ìîäåëü mSUGRA/MSSM , âáóäî- âàíà â ïàêåò PY THIA6. Ðîçãëÿäàëîñü äâà êðèòåði¨ âiäáîðó äëÿ ïîøóêó SUSY ïîäié. Çà äîïîìîãîþ ãåíåðàòîðiâ MADGRAPH i POWHEG áóëè îöiíåíi ôîíè, îáóìîâëåíi ïðîöåñàìè Ñòàíäàðòíî¨ Ìîäåëi. Ïîêàçàíî, ùî ç ðiâíåì äîâiðè 95% îòðèìàíi ðåçóëüòàòè çíàõîäÿòüñÿ ó âiäïîâiäíîñòi iç ïåðåäáà÷åííÿìè Ñòàíäàðòíî¨ Ìîäåëi i â ìåæàõ Emiss T > 200 i M inc eff > 600 åôåêòè íîâî¨ ôiçèêè íå ñïîñòåðiãàþòüñÿ. 12

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