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Exploring New Heavy Gauge Bosons at CMS

Discover the potential of new heavy gauge bosons in solving Standard Model limitations through extensions like W', Z', and more models. Explore event selections, backgrounds, and scenarios examined at CMS. Limits and constraints set for various models with mass prediction and event selection criteria.

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Exploring New Heavy Gauge Bosons at CMS

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  1. New Heavy Gauge Bosons at CMS Claudia-Elisabeth Wulz On behalf of the CMS Collaboration Institute of High Energy Physics Vienna Austrian Academy of Sciences 7 July 2012

  2. New heavy gauge bosons To solve known shortcomings of the Standard Model, extensions have been proposed. The SM gauge group SU(3)CxSU(2)LxU(1)Y can be extended by: - An extra U(1) group, giving rise to a neutral heavy vector boson Z’ - An extra SU(2) group, giving rise to a charged heavy vector boson W’ Model examples: - Sequential Standard Model (SSM): new bosons have similar couplings as W, Z in SM - Left-right symmetric models: SU(2)LxSU(2)R - Superstring-inspired E6 models: E6 SO(10)xU(1)ySU(5)xU(1)cxU(1)y. Only one linear combination G leads to particles at the TeV scale: G = cosq U(1)c- sinq U(1)y. q = 0: y-model - More complicated scenarios predict a tower of new gauge bosons (Wn, Zn, or gravitons Gn), such as technicolor or extra dimension models.

  3. Z’ l+l-(l= e,m) Many Z’ models predict narrow resonances decaying to dileptons. Event selection: ET (e1,e2) > 35 GeV, pT(m1,m2) > 45 GeV, plus isolation criteria Backgrounds: - Z/g*, tt, tW, VV, Z tt, multijets with ≥1 jet reconstructed as lepton - estimated by fitting data with appropriate function _ M(Z’SSM) > 2590 GeV M(Z’y) > 2260 GeV Rs = sll(Z’)/sll(Z) CMS PAS EXO-12-015, hep-ex 1206.1849, CMS PAS EXO-11-019

  4. Z’ tt There are non-universal scenarios in which the Z’ couples preferentially to third-generation fermions. Final states studied: tetm, teth, tmth, thth. n’s in final state do not allow to reconstruct mass of tt system. Event selection: 2 t candidates with pT between 15 and 35 GeV, h < 2.1,isolation criteria, no b-jets Backgrounds: DY Z tt, W+jets, tt, VV, QCD Backgrounds areestimatedfromdatawherepossible. _ Effectivevisible mass tetm thth M(Z’SSM) > 1.4 TeV M(Z’y) > 1.1 TeV hep-ex 1206.1725 submitted to PLB CMS PAS EXO-11-031

  5. W’ lnwithout W-W’ interference Models studied: - W’SSM with SM-like couplings, with W’SSM tb allowed - Kaluza-Klein W2KK in split UED framework Event selection: ~back-to-back isol.l+ETmiss, energy-balanced Backgrounds: Wln, QCD, tt+single top, DY, VV from data W’en _ W’mn M(W’SSM) > 2.8 TeV M(W2KK) > 1.25 TeV (m = 0.05 TeV) M(W2KK) > 3.3 TeV (m = 10 TeV) CMS PAS EXO-12-010 ICHEP, July 2012

  6. W’ lnwith W-W’ interference A left-handed WL’ can interfere with the W. Studies were performed with 7 TeV data. Limits for a WR’ have also been derived. M(WR’SSM) > 2.5 TeV M(WL’SSM) > 2.63 TeV (constructive interference) M(WL’SSM) > 2.43 TeV (destructive interference) hep-ex 1204.4764 submitted to JHEP

  7. W’tb • WR’ decays to leptons suppressed if M(nR) > M(W’)search in hadronic final states important. Decay chain: W’ tbWbblnbb. • Event selection: isol.e(m) withpT > 35(32) GeV, ETjet1(jet2) > 100(40) GeV, ≥ 1 b-tag • Backgrounds: tt+single top, W(ln)+jets, Z/g* (ll)+jets, QCD, VV _ New BDT analysisfor signal/background discrimination with ~50 variables (object and event kinematics, top reconstruction, angular correlations). Comparison of BDT and invariant mass analyses CMS PAS EXO-12-001

  8. W’tb Most general model-independent LO Lagrangian for a W’ coupling to SM fermions: M(WR’) > 1.85 TeV Mass limit and constraints of W’gaugecouplingfor a set of left- and right-handedcouplingcombinationshavebeenset: Contours of W’ mass at whichtheobserved 95% CL cross-sectionupperlimitequalsthepredictedcross-section

  9. W’td _ • Tevatron measurement of forward-backward asymmetry at high tt inv. mass • Possible explanation: light W’ • N(W’-) > N(W’+) at LHC -> aids in reconstructing the W’ Decay chain: pp tW’ttd, with semileptonict-decays plus a jet in final state. Difference of yieldsfort-+d and t++d invariant mass distributions (charge assignment from leptonic top decay): hep-ex 1206.3921, CMS PAS EXO-11-056

  10. W’td M(W’) > 839 GeV

  11. W’, GRSVZ wide jet + lepton pair l • W’SSM ZW lljj, GRS ZZ lljj • 2-fermion systems boosted for heavy resonance • Event selection: • based on high-pT Z candidates from lepton pair and wide jet well separated from leptons • Backgrounds: from data • W+jets, tt,gV+jets, Z/g*+jets, ZZ, VV+jets l W’, G Z W, Z merged jet 95% CL exclusion limits _ CMS PAS EXO-11-081 ICHEP, July 2012

  12. Conclusions • CMS has studied scenarios for new heavy gauge bosons. • Although no signals for new physics have been found yet, • limits on masses and other quantities have been set. • Details may be found here: • https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsEXO • We are looking forward to more LHC data! ICHEP, July 2012

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