1. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 1 Search for Charged Higgs at the LHC Ashfaq Ahmad (Stony Brook)

2. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 2 Contents  Introduction  Charged Higgs studies in ATLAS and CMS  Search for the light charged Higgs bosons with H ± ->  in top quark decays  Search for heavy charged Higgs bosons with: H ± ->  decay channel H ± -> tb decay channel  Discovery reach

3. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 3 LHC experiments

4. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 4 ATLAS and CMS Detectors ATLAS as of July 2007 CMS as of Jan 2007

5. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 5 Charged Higgs Boson  MSSM, the minimal supersymmetric extension to SM requires two Higgs doublets  Give masses to the up and down type quarks and leptons  Corresponds to 8 degrees of freedom  3 of which are absorbed as Goldstone bosons to give mass and longitudinal components to the W ± and Z  Leaves five physical states (Higgs particles) Two neutral scalars, h 0, H 0, a pseudo scalar A 0 and a pair of scalar charged Higgs H ±  At tree level all masses and couplings can be expressed as a function of two parameters:  The pseudo scalar Higgs boson mass m A  and tan  the ratio of the vacuum expectation values of the two Higgs doublets

6. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 6 Charged Higgs at the LHC  Production modes for heavy charged Higgs:  Below top mass:  t  H + b LHC is a top factory, NLO ttbar cross section ~833pb  over 8M ttbar pair in one year (10fb -1 )  Above top mass:  Via gluon fusion, gg  tbH +  And gb  tH +  Decay modes:  H + , H +  tb, H +  cs

7. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 7 Search for Charged Higgs below M top (1)  In MSSM charged Higgs may be produced in top decay if kinematically allowed via ttbar → W + bH - b  If M H + < (M top – M b ) the decay t → W + b together with t → H + b saturates the top decay width in the MSSM  BR is large at SMALL and LARGE tanβ (for a given M H ) but it has a pronounced minimum at tanβ ~√m top /m b ~7.5  BR(t  H±b)~m top 2 cotan 2 β+m b 2 tan 2 β LEP excludes 0.5 < tan  < 2.4

8. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 8 Search for Charged Higgs below M top (2)  Assuming a heavy SUSY spectrum a charged Higgs will decay exclusively into SM particles and below M top the braching ratio H +  is~100%  Main channels of interest: H ± decay BR. into different final states for tan  = 20 H + DecayW Decay ,  hadqq ,  hadll ,  lepqq

9. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 9 ttbar → H - bW + bbar, H - →  had , W → qq (1)  Exploited the difference between signal and ttbar  m H+ > m W so diff in p T and E T miss  Spin (helicity effect): scalar H +, vector W  Event Selection  Tau+MET ot Jet+MET trigger  Tau jet p T > 25 GeV  2 b jets, p T j1 >35GeV, p T j2 >20GeV  isolated lepton veto  E T miss > 45 GeV  W/top reco. in 20/40 GeV mass window  ttbar event pattern: cuts on  between two reco tops and the ratio between their pT(< 2)  p T  /p T b > 0.8  transverse mass (M T ) + tau p T > 30 GeV  Main background  ttbar, QCD ATL-PHYS-2003-038

10. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 10 ttbar → H - bW + bbar, H - →  had , W → qq (2) Sig/bkgStandard cuts M T (H + ) >80GeV p T (tau) >3 0GeV m H+ = 85GeV5100- m H+ = 127GeV42002000 m H+ = 140GeV29001700 m H+ = 160GeV410240 ttbar2300350 QCD200 Expected events @ 10fb -1, tan  = 30  significant ttbar background with standard cuts  Masses above 113 GeV are passed through a final event selection on the charged Higgs transverse mass, and tightening of the tau p T cut

11. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 11 ttbar → H - bW + bbar, H - →  had , W → qq (3)  The dip between tanβ ~ 5 and tanβ ~10 is covered by hadronic channel  A high significance is obtainable for all tan  and m H+ < 150 Leptonic channel (W  l  ) was studied long time ago(ATL-PHYS-94-053). This channel features a high Pt lepton for triggering, but the presence of two neutrinoes exludes any mass extraction possibilities. 5  line @30fb -1 is also shown. Results given here are from ATLAS fast simulation. Full simulation studies are in progress

12. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 12 ttbar → H + bW - bbar, H + →  had , W → l  (1)  Enhanced tau-lepton rate in ttbar decays  mass of H ± cannot be directly reconstructed because several neutrinos are produced in the final state  Excellent  -ID is a must!  Measurement of significance of the event excess with an isolated  with respect to rate foreseen by SM BACKGROUNDS intrinsic Due to fake tau’s W+jets SIGNAL

13. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 13 ttbar → H + bW - bbar, H + →  had , W → l  (2)  Exploited difference between signal and ttbar  m H+ > m W, diff in p T and E T miss  Spin: scalar H +, vector W  Event Selection  Triggered lepton  3 jets with E T > 40GeV  At least one b-tagged jet  Q(l)+Q(  )=0  Tau jet E T > 40GeV  P lead track / E  > 0.8, to exploit opposite helicity correlations in the taus coming from H + and W  E T miss > 70GeV Sig/bkg  xBR(fb)Events @ 10fb -1 m H+ = 140GeV10700510 m H+ = 150GeV5060254 m H+ = 160GeV183092 tt → l  bb2.6x10 4 516 tt → l  l  bb4.0x10 4 293 tt → l  qqbb2.5x10 5 366 W+3jets, W → l  8.4x10 5 107 CMS Note 2006/056

14. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 14 Discovery potential (3)  5  contour in m H ±, tan  plane for the light Charged Higgs with and without systematic uncertainties  tan  > 50, covered up to top mass  Due to systematic uncertainties there is a decrease of 5-10GeV in the observable charged Higgs mass for tan  < 50  Charged Higgs mass of 170GeV observable at tan  ~ 100 CMS Note 2006/056 I am working on this channel for ATLAS. Preliminary results expected in few weeks.

15. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 15 Search for Charged Higgs above M top  Above top mass:  Via gluon fusion, gg  t bH +  And gb  t H +  BR(H +  tb)~0.8-1  H +  tb results in complex final states  Having 3 or 4 b jets  Crucial to supress very large kinematically similar ttbar+jets background H + DecayW Decay ,  hadqq tbl  & qq  xBR (pb) Channels of interest:

16. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 16 gb/gg → t(b)H + → Wb(b) tb → lυb (b) jjbb (1)  Event Selection  Isolated muon, p T > 20GeV  At least 3(4) b jets  At least 5(6) jets with p T > 25GeV  Kinematic fit imposing mass constraints on both W,s and top quarks  LH to suppress combinatorial background  3(4)b-tags, with LH based secondary vertex algorithm  Background  ttbar+b, ttbar+jets  High combinatorics CMS Note 2006/109 SN-ATLAS-2004-042 CMS: S/B ratio after selection ~1% for m H+ = 300 GeV

17. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 17 Discovery potenial (2) CMS 3 b-tags CMS 4 b-tags  No sensitivity in MSSM space even with very low systematic uncertainties  Similar conclusions from ATLAS FAST simulation studies 30 fb -1

18. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 18 gb/gg → t(b)H + → qqb(b)  had  (1)  Event Selection  One  -jet, P T > 100 GeV  At least three non  -jets(at least one b-tag)  No more than one hard b-jet (|η| 50 GeV)  Reconstruct W/top in 25 GeV mass window  E T miss > 100 GeV  cut on the azimuthal opening angle (Δφ) between the  -jet and missing P t. Require Δφ > 1.1  Veto on isolated leptons  P lead track / E  > 0.8  Main background  ttbar, QCD, W+jets

19. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 19 Discovery potenial (2) with systematics  without systematics  Background: FAST simul. without systematics ATLAS CMS  systematics included  Background: Full simul.  promising channel for heavy charged Higgs

20. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 20 CMS and ATLAS Discovery Potential …  Fast simulation  ATLAS full simulation studies in progress. Results by the end of 2007  Charged Higgs covered at LHC for m H+ < m top  Heavy Charged Higgs sensitive at high tan  ATLASCMS Full simulation 300 fb -1 30 fb -1

21. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 21

22. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 22 Conclusions  Both ATLAS and CMS are sensitive to light charged Higgs below top mass  Discovery potential @ 30fb -1  Heavier charged Higgs would have to wait for the high luminosity mode  Accessible at high tan   The intermediate tan  region in MSSM space is not covered by any SM decay  H +  is the best H + discovery channel at the LHC

23. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 23 backup

24. 29 August, 2007 Ashfaq Ahmad, Search for Charged Higgs at the LHC 24