Research and Study of SUSY 藏京京 1

Summary of Supersymmetry Supersymmetry (SUSY) is a symmetry that relates elementary particles of one spin to another particle that differs by half a unit of spin and are known as superpartners. In other words, in a supersymmetric theory, for every type of boson there exists a corresponding type of fermion, and vice-versa. Minimal Supersymmetry Standard Model(MSSM) contains the minimal extension of the Standard Model particle. mSUGRA Because of unknown mechanism for breaking SUSY, We will only consider a version called mSUGRA, which guarantees universality of gaugino and scalar masses and of trilinear couplings at a high scale. 2

mSUGRA parameters and spectrum Five free parameters: m 0,m 1/2,A 0,tanβ, sign(μ) Then the sparticle spectrum, decay branching ratios and production cross sections can be derived. gaugino mass parameters: gluino mass is equal to M 3, neutralinos (i=1-4) and chargino (i=1-2) masses are obtained after diagonalising their mass matrices which are a function of M 1,M 2, μ. The sfermions of the first two generations: Third family scalars mass are more complicated. Yukawa couplings,off-diagonal elements. 3

Sparticle Production and Cascade Deacy Region 1: gluinos heavier than any of squarks Region 2: some squarks heavier, other are lighter than gluino. of the first two generations are excepted to be among the heaviest squarks and the (and )among the lightest. Region 3: gluinos lighter than any of the squarks. Regions of the m0 versus m1/2 plane showering the production cross sections and with main squark and gluino decays 4

Test Point for mSUGRA test CMS points are indicate by stars and the point used in the CMS DAQ TDR by triangle mSUGRA parameter values for the test points.Massed are given in units of GeV 5

Property of 14 Points 6

Cross Sections for the test points in pb at NLO(LO) for PROSPINO1 7

Inclusive Analysis with missing transverse energy and jets Search for the production and decay of gluinos and squark LM1 test-point(LO cross section 49fb) Events selection: Major backgrounds and uncertainties: 8

Inclusive analysis with missing transverse energy and jets Selected SUSY and Standard Model background events for 1 fb -1 Standard Model background components and uncertainties for 1fb -1 5σ observation of low mass SUSY at LM1(gluino mass 600GeV/c 2 ) is achievable with about 6pb -1 in events with large missing energy plus multi- jets.(significance computed with ScPf) 9

Inclusive muons with jets and missing transverse energy (at least one muon) Signal selection  leading muon p T >20GeV/c (good reconstruction efficiency)  leading muon isolated with less than 10GeV of calorimeter energy with a cone of radius R=0.3 (reduce fake muons effects)  three leading jets E T >50GeV (good reconstruction efficiency) Backgrounds Considered  QCD dijet   electroweak single-boson  electroweak dibosons Optimized Cuts By GARCON  Assuming 10 fb −1 of collected data, this set of cuts would expect to select a total of 2.54 background events from the Standard Model and 311 signal events from the mSUGRA LM1 benchmark signal point. 10

CMS discovery reach CMS discovery reach contours in the m 0 -m 1/2 plane using inclusive muons with jets and missing energy for 10 fb -1, 30fb -1 and 60 fb -1 including systematics 11

Inclusive analysis with same sign dimuons Signal Selection  muon dimuon trigger efficience 98%, reconstructed muon separated ΔR ≥ 0.01 from the other one. muon track fit ;hit number >13; same sign &&P T >10GeV/c  jet jet number ≥ 3 &&E T > 50GeV (final optimal cut-set: ) 12

Inclusive analysis with same sign dimuons Background Considered QCD dijet ( ) electroweak signal boson( ) electroweak dibosons 13

CMS inclusive reach CMS reach contours(systematic uncertainties included) in the (m0,m1/2)plane for SUSY processes involving two prompt same-sign muons for L = 1fb -1,10fb -1,30fb -1, 100fb -1. The other mSUGRA parameters are fixed to tanβ=10,μ>10 and A 0 =0 14

Inclusive analysis with opposite sign dileptons Signal originate from the decay in the cascade decays of squarks and glunios. The dilepton invariant mass distribution for this decay is expected to have a triangular shape with a sharp upper edge. Signal selection:  the Level-1 and HLT path that requires a single isolated lepton(muon or electron);  at least two same-flavour opposite-sign(SFOS) isolated leptons(e or μ )with p T >10GeV/c and ∆R ll ≥0.2 and 0.15 for ee and μμ,respectively where the ∆R ll is the distance of two leptons in the η-φ space.   at least two jets with pT ≥ 100 and ≥60GeV/c within 15

Inclusive analysis with opposite sign dileptons Background considered: Cross section at NLO, selection efficiencies and number of events surviving cuts for signal and background processes 16

Results for point LM1 the dilepton final state, assuming tan β = 10,A = a, μ>0 and I,10,30,fb-1 intergrated luminosity (statistical uncertainties only) 5σ discovery reach for tan β =10 take into account background systematic uncertainties 17

Inclusive analyses with ditaus Signal originate from in gluino and squark cascade decay. Events selection:  Missing E T >150GeV (remove large fraction of SM bg)  At least two tau candidates  At least two jet with E T > 150GeV  ∆R between any pair of tau’s should be samaller than 2 Background considered  W and Z production and t ¯t which final states may contain several taus and jets  Because of its huge cross section (1.3 ·10 −4 mb) QCD jet production is also considered.(an important source of fake taus and fake missing transverse energy due to imprecision in jet energy measurement.) 18

Discovery potential of mSUGRA with ditaus final states 19

Other Chanel List Higgs: supersymmteric Higgs boson h0 -> so at least two b-tagged jets, miss E T and multiple jets Z 0 : with Z 0 decays into SFOS top: 20

Summary of the reach with inclusive analyses 21

List of other organization’s work 1.Bbar+multi-jets+MET Tanja Rommerskirchen University of Zurich (Switzerland) 2.Ditau+hadronic-jets+MET GEORLACH Ulrich IPHC Strasbourg (France) 3.Full hadronic channel Christian Autermann (Germany) 4.Higgs K. Huitu Helsinki Insitute of Physics HIP (Finland) 5.4 leptons Pedro Ribeiro, LIP-Lisbon (Portugal) Malgorzata Kazana, SINS- Warsaw(Poland) 6.dilepton_+jets+MET (measurement of X2->x1ll ) Georgia Karapostoli (Univ of Athens) Paris Sphicas (CERN) 7.e+ jets + MET Peter Wittich Cornell University (USA) 8.Muons + Jets + MET Philipp Biallass RETH Aachen University (Germany) 22