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SUSY Higgs at the LHC - Cosener's April 2004 1 SUSY Higgs at the LHC C. H. Shepherd-Themistocleous RAL UK HEP Forum, Coseners, 25 th April 2004.

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Presentation on theme: "SUSY Higgs at the LHC - Cosener's April 2004 1 SUSY Higgs at the LHC C. H. Shepherd-Themistocleous RAL UK HEP Forum, Coseners, 25 th April 2004."— Presentation transcript:

1 SUSY Higgs at the LHC - Cosener's April SUSY Higgs at the LHC C. H. Shepherd-Themistocleous RAL UK HEP Forum, Coseners, 25 th April 2004

2 SUSY Higgs at the LHC - Cosener's April Introduction Why SUSY: Provides mechanism for EWSB. (Only possible if SUSY broken) Unifies gauge couplings ~ GeV Solves naturalness (hierarchy) problem Higgs physics (MSSM) Two independent Higgs doublet fields required. Direct consequence of supersymmetric transformations that relate fermions and bosons. vev minimize potential d u tan

3 SUSY Higgs at the LHC - Cosener's April REWSB - (Driven by quantum corrections) 8 degrees of freedom 5 physical states h 0, H 0 (CP-even), A 0 (CP-odd), H ± 3 longitudinal components of W ±,Z 0 From mass matrices (tree level) – 6 parameters - 4 masses, tan, (mixing parameter in CP even mass matrix) – Only 2 independent e.g. m A, tan – Radiative corrections introduce more parameters )( )( (cos , 2 1 hHA hZh wA H AZZAZAhH mmm mmm mmm mmmmmmm

4 SUSY Higgs at the LHC - Cosener's April Mass limits 2cos 222 Zh MM Gives upper bound on mass of lightest higgs h 0 Consequence of Higgs quartic self couplings depending on electroweak gauge couplings. Not free parameters as in the SM. (m 2 sm = 1/2 Radiative corrections in MSSM. (SUSY breaking) Incomplete top stop loop cancellation most important ~ m t 4, ln m stop, stop mixing Extensions of MSSM ( Quiros & Espinosa hep-ph ) Keep gauge coupling unification Keep perturbative up to unification scale For arbitrary matter content M h < 210 GeV GeVM h 130 ~ ~

5 SUSY Higgs at the LHC - Cosener's April Relationship between masses

6 SUSY Higgs at the LHC - Cosener's April Couplings Similar to SM like couplings. Modified by 0 tan 1/tan A0A0 cos( - )cos /cos sin /sin H0H0 sin( - )sin /cos cos /sin h0h0 111SM H gVgV gdgd gugu Can be generated by H.O. loops Decoupling limit: m A >> m Z Tree level h 0 couplings SM for all tan Large tan bbH, bbA enhanced by tan relative to SM VVH remains negligible Radiative corrections decoupling delayed by tan 0 )( )( (cos hHA hZh mmm mmm HH A mmm 0 tree level )sin(tancos( cos

7 SUSY Higgs at the LHC - Cosener's April SM production processes modified by couplings (tan ). Large tan bb coupling important. gg associated production bb Sparticles can also contribute Note H 0 VV couplings ~ cos( therefore suppressed for large tan VBF production channel not significant for H 0 at large tan Useful decay channel H 0 ZZ lost Plots: M SUSY = 1TeV, = 1TeV, NLO QCD included m h/H (GeV) m h/H (GeV) cross-section (pb) Notice no tt threshold bump MSSM Higgs production: h 0 / H 0

8 SUSY Higgs at the LHC - Cosener's April m A (GeV) cross-section (pb) Large tan same effect: A 0 bb coupling important. gg A 0 associated production A 0 bb Plots: M SUSY ~ 1TeV, = 1TeV NLO QCD included A 0 does not couple to vector bosons at tree level. No VBF channel MSSM Higgs production: A 0

9 SUSY Higgs at the LHC - Cosener's April If m(H + ) < m t - m b t b H + competes with SM t W + b produced in tt production followed by t decay (Can be up to 0.5 func. tan If m(H + ) > m t gg, qq tbH gb tH ± Radiation off 3 rd generation quark MSSM Higgs production: H +

10 SUSY Higgs at the LHC - Cosener's April MSSM Higgs Decays Decay pattern depends on region of parameter space and SUSY parameters m A >>m Z M SUSY large (~1TeV) decoupling limit h h SM M SUSY light (e.g. 200GeV modified. Direct to SUSY + contributions to 1- loop decay rate h 0 gg possible. In both cases H 0, A 0, H +/ ~ mass degenerate BR ~ tan m A < 150 GeV tan ll higgs masses GeV. (Intense coupling regime.) All H produced in many channels. Signal for one bg for another Suppression of HVV coupling results in smaller widths than SM.

11 SUSY Higgs at the LHC - Cosener's April MSSM Higgs Decays: h 0 /H 0 SUSY params: M SUSY = 1TeV, M 2 =1 TeV, X t =2.4 M SUSY enhanced relative to SM. Radiative corrections significant at large tan HVV suppression with increasing tan tt channel dominant for large H mass and small tan At large tan bb and dominate for all values of m H

12 SUSY Higgs at the LHC - Cosener's April Different choice of SUSY parameters shows SUSY final states can be important and even dominant. If to LSP invisible Higgs decay.

13 SUSY Higgs at the LHC - Cosener's April MSSM Higgs Decays: A 0 SUSY params: M SUSY = 1TeV, M 2 =1 TeV, X t =2.4 M SUSY BR to bb, and tt behave as for CP even neutral higges. No tree level AVV coupling Decays to sparticles can be significant

14 SUSY Higgs at the LHC - Cosener's April MSSM Higgs Decays: H + SUSY params: M SUSY = 1TeV, M 2 =1 TeV, X t =2.4 M SUSY tb dominant if allowed otherwise No HWZ coupling at tree level sparticle decay can be significant at high mass

15 SUSY Higgs at the LHC - Cosener's April Large variety of observation modes SM like : – h, bb ( tth, h bb) – H 4 (strongly suppressed ) MSSM specific : – A/H,, tt – H hh – A Zh – H, tb If SUSY accessible: – H/A – 2 0 h 1 0 Useful decay modes

16 SUSY Higgs at the LHC - Cosener's April Lightest MSSM higgs: h 0 Search for in SM like channels. VBF channels useful.

17 SUSY Higgs at the LHC - Cosener's April H 0 /A 0 decays Provides best reach large tan : +, + had, had + had had+had final state: Backgrounds: QCD ( muli-jet fake ) ; Z/ * tt ; W+jet, W. Requires hadronic trigger Large associated production allows good rejection with b tag. jet (1-, 3- prong) tagging, lifetime Potential SUSY background. - decays. negligible b tagging QCD ~ 10 6 rejection Mass resolution ~ 15% ~ Exploit bbH 0 /A 0 production

18 SUSY Higgs at the LHC - Cosener's April H 0 /A 0 decays Enhanced bbH/A production at large tan make this possible c.f. SM Backgrounds: Z, * reject using b tagging t t Wb, W reject using central jet veto Not able to resolve A and H peaks. m ~ 1% m H - m A | ~ 2GeV here

19 SUSY Higgs at the LHC - Cosener's April H 0 /A 0 parameter space coverage N.B. LEP tan limit can be significantly reduced e.g. M SUSY =2TeV, m t =180GeV & theory error in m h max 5 reach

20 SUSY Higgs at the LHC - Cosener's April H ± decays Provides clear signature for BSM physics. Production: – m H ± < m t : tt, t H ± b – m H ± > m t : gb t H ±,gg tbH ±, qq H ± Backgrounds: tt ; Wtb, W Signal : Look for lepton from top + had Spin correlations from H harder than from W. Require 80% jet energy carried by + Plot transverse mass. (missing >1 ) – Signal endpoint ~ m H – Background endpoint m w

21 SUSY Higgs at the LHC - Cosener's April reach for H ± N.B. The 2001 joint TLAS + CMS compilation had an error in the cross section for the H + tb channel. The correction results in a lower reach for this channel.

22 SUSY Higgs at the LHC - Cosener's April Plane fully covered (no holes) at low L (30 fb -1 ) Main channels : Two or more Higgs can be observed over most of the parameter space disentangle SM / MSSM N.B. LEP tan limit can be significantly reduced e.g. M SUSY =2TeV, m t =180GeV & theory error in m h max LHC discovery potential for MSSM Higgs bosons 5 reach

23 SUSY Higgs at the LHC - Cosener's April Higgs observable 3 Higgs observable 2 Higgs observable 1 Higgs observable Only SM-like h observable here if SUSY particles neglected.

24 SUSY Higgs at the LHC - Cosener's April SUSY particle effects If SUSY kinematically accessible Higgses can decay directly to or come from decays of SUSY particles Light SUSY particles suppress or enhance loop induced production or decays Sparticle decay modes can compete with SM modes Also possible h 0 LSP, invisible for R parity conservation Further source of Higges from cascade decays of heavy SUSY particles little cascade big cascade

25 SUSY Higgs at the LHC - Cosener's April A 0 /H 0 l + l - l + l - enables good S/B Large parameter space to consider. Mass Plot M A =350 GeV, tan =5, M 2 =2M 1 =120 GeV, = 500 GeV, M q,g =1 TeV M l = 250 GeV Backgrounds: SM (ZZ, Zbb,Zcc, tt) and SUSY ( q,g Selection: Lepton isolation, E T miss, jet veto (q,g large jet mult. av. 5) ~ ~ ~ ~ ~ ~ ~ Production B.R. A/H 4 l X

26 SUSY Higgs at the LHC - Cosener's April ATLAS have performed a scan of SUGRA parameter space. Plot: Projection in M A, tan plane 5s contours 30 fb -1 : m 0 = 50,100,150, sign( ) = +1 m 1/2 = GeV, tan = , A 0 =0 Useful for filling low tan hole.

27 SUSY Higgs at the LHC - Cosener's April Invisible Higgs H LSP decays possible. Use production channels like VBF (Hqq), WH, ZH, ttH VBF signal Forward and backward jets + large missing p t in central region. Background: Z jet jet, Z W jet jet, W l miss l ), QCD jets + escaping particles Selection: F & B jets Missing E T Central jet veto Lepton veto Requires dedicated trigger 2 jets + E T miss

28 SUSY Higgs at the LHC - Cosener's April MSSM Higgs parameters Couplings - methods as SM Determination of tan eff from signal rates. ( MSSM loop corrections) Production at large tan tan 2 (gg bbH/A, gb tH ±, gg tbH) Obtain tan from number of signal events require: Luminosity error Theoretical uncertainly in Error in selection efficiency BR to final state ( e.g. H/A approx. const for large tan ) ATLAS TDR

29 SUSY Higgs at the LHC - Cosener's April Where do we go from here? MSSM Higgs decays to SM particle well explored. > 1 Higgs accessible over large part of parameter space. Some studies of effects of SUSY particles in production and decay. Need to more systematically explore. Improvements in parameter extraction - tan Improvements in understanding of backgrounds. Non-minimal SUSY models. e.g. effects of non-zero phases, CP violation...

30 SUSY Higgs at the LHC - Cosener's April Backup slides

31 SUSY Higgs at the LHC - Cosener's April From ATLAS physics TDR


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