1. A/H  and A/H  decays at the LHC Outline of the talk: The LHC and ATLAS,CMS MSSM A/H Higgs production A/H  A/H  Conclusions HEP2003 Europhysics Conference Aachen, Germany, 17-23 July 2003 Silvia Arcelli Univ. of Bologna and INFN for the ATLAS and CMS Collaborations Covering Abstracts: Abs 674: “Search for A/H   with CMS” Abs 421: “Studies of Lepton Flavor Violation with ATLAS”

2. EPS03 Meeting, 17 July 2003, Aachen 2 A/H  and A/H  at LHC, S.Arcelli The LHC and ATLAS,CMS detectors pp at 14 TeV, collision rate 40 MHz, with a design luminosity L= 10 34 cm -2 s -1. First physics run planned for Aug 2007 at L= 2 x10 33 cm -2 s -1 ATLAS and CMS detectors equipped with high precision tracking systems, high resolution ECAL and hermetic calorimetry, large acceptance muon spectrometers to ensure: Efficient b-tagging and  identification Good jet and missing E T resolution Precise muon ID & reconstruction

3. EPS03 Meeting, 17 July 2003, Aachen 3 A/H  and A/H  at LHC, S.Arcelli MSSM A/H Production Golden channel at LHC is A/H  (BR ~10%), but other rare/non-standard decays can be effective probes of the MSSM Higgs sector and of physics beyond the SM: A/H  : very small branching ratio (~3 ×10 -4 ) but very clean signature A/H  : search for LFV effects involving the 2 nd and 3 rd generation Predominantly via gluon fusion and bbA/H associated production bbA/H production and decays to down type fermions dominant at high tan  A/H degenerate over most M A -tan  plane

4. EPS03 Meeting, 17 July 2003, Aachen 4 A/H  and A/H  at LHC, S.Arcelli A/H  Decay hardly observable at LHC in case of SM Higgs (s,vLHC), but low branching ratio is compensated by the cross-section enhancement in the MSSM : Although BR(A/H  )/BR(A/H  )~ 2 10 -3, discovery potential in  channel enhanced by very efficient muon ID+reconstruction (>90%) and invariant mass  resolution  M  )= 1-2%, ~10 times better than in  Excellent di-muon mass resolution allows for a precise measurement of the Higgs mass and a direct measurement of the Higgs width for high tan   Feasibility studies: ATLAS: ATLAS physics TDR CMS: CMS-NOTE-98-039, and full simulation+realistic reconstruction study, results presented in this talk (CMS preliminary) (L. Bellucci, “MSSM Neutral Higgs Bosons Search with CMS in the  channel”, PHD Dissertation, Universita’degli Studi di Firenze)

5. EPS03 Meeting, 17 July 2003, Aachen 5 A/H  and A/H  at LHC, S.Arcelli bbA/H associated production channel, assuming low luminosity conditions. Search strategy based on clean signature from: high Pt, isolated muons Sharp di-muon mass peak b-tag of the associated production Main Background processes: Drell-Yan production Z/  *  bbZ/  *  bb  (~ 2% of inclusive Drell-Yan ) other potential backgrounds like bb,cc, WW,ZZ   +X negligible. top pair production tt  bb bbA/H  bb  in CMS

6. EPS03 Meeting, 17 July 2003, Aachen 6 A/H  and A/H  at LHC, S.Arcelli Two isolated muons with P T >10 GeV, efficiency ~ 87 % Mass resolution  1.5 %,  H,A ~ O(1-10 GeV) depending on M A, tan  M  (GeV) MA=  150 GeV tan  = 30  H,A ~ 3 GeV Di-muon system: With cuts on the di-muon system alone, 5  signal observable only with integrated luminosity >100 fb -1 b-tagging allows to substantially improve the S/B ratio!  M  (GeV) MA=  150 GeV tan  = 30 L= 20 fb-1 CMS preliminary

7. EPS03 Meeting, 17 July 2003, Aachen 7 A/H  and A/H  at LHC, S.Arcelli b-jets from associated production are soft, low efficiency for jet reconstruction (typical efficiency for  1 jet ID+b-tag ~ 20%) Event b-tag used, relaying on a combination of different variables: Number of secondary vertices 2,3-d track impact parameter impact parameter significance  b-tag ~40%, factor ~10 rejection on Z/  * B-jet E T (GeV) N. Of secondary vertices B-Tagging: MA=  150 GeV tan  = 30 CMS preliminary

8. EPS03 Meeting, 17 July 2003, Aachen 8 A/H  and A/H  at LHC, S.Arcelli b tagging not effective against top background, which contains 2 hard central jets from b’s ; use a jet veto and require small missing E T : No jet with E T >30 GeV E T miss < 40 GeV Top background suppressed by factor ~ 20,  signal ~ 70% Top Rejection: Missing E T (GeV) jet E T (GeV) Probability/dE T jet Events/dE T jet CMS Preliminary

9. EPS03 Meeting, 17 July 2003, Aachen 9 A/H  and A/H  at LHC, S.Arcelli Precise measurement of A/H mass, expect dM/M~0.2 % for L=60 fb-1 For tan  >20, where the natural Higgs width dominates over the detector resolution, can directly measure   and have an independent constraint on tan  in addition to that from event rates L= 20 fb-1 M  (GeV) Final selection efficiency ~ 22% ~ independent on the Higgs mass. Fitting with a gaussian (for signal) + exponential (for background): Mean  = 150.7±0.6 GeV  Width  = 3.7±0.7 GeV With full di-muon mass resolution/calibration this channel should allow for : S /  (S+B) ~ 7 Events/GeV M  (GeV) MA=  150 GeV tan  = 30 CMS preliminary

10. EPS03 Meeting, 17 July 2003, Aachen 10 A/H  and A/H  at LHC, S.Arcelli Substantial portion of the M A -tan  plane covered already with 20 fb -1. Comparable results obtained in ATLAS TDR study Same strategy can be extended to h/A search for M A [105-125] GeV (h,A degenerate), requires maximal luminosities (recent studies by ATLAS, ATL- PHYS- 2002- 021, ATL- PHYS- 2003- 013 ) M   (GeV) ATLAS A/H , 5  discovery reach tan  CMS preliminary

11. EPS03 Meeting, 17 July 2003, Aachen 11 A/H  and A/H  at LHC, S.Arcelli A/H  M   (GeV) BR Observation of atmosferic    neutrino oscillations with maximal mixing and implies lepton number non-conservation  expect LFV decays One possibility to search for LFV effects at the LHC is the decay A/H   study done by ATLAS. (ATLAS-COM-PHYS-2002-031) Two different (Type III) 2-Higgs doublet models (a,b) were considered: BR(A/H  2   2m   m   BR(H SM    depends on LFV coupling ,  and widths  H SM,  A/H Model a,b BR(A/H  for   = 1

12. EPS03 Meeting, 17 July 2003, Aachen 12 A/H  and A/H  at LHC, S.Arcelli Jet veto against W+jets, b-jet veto against tt (gluon fusion production is considered) In hadronic channel select 1-prong decays (collimated jet with single energetic hadron) to suppres W+jets background  E T miss hadron (tau jet), electron   Search performed using hadronic and e tau decays. Background expected from Z/  *, tt, WW,WZ production and W+jets (hadronic channel): High p T,isolated , muon harder than tau decay product with large opening angle in transverse plane (2-body decay). Tau higly boosted, require E t miss collinear to visible tau decay product and p T  >50 GeV p T  = p T  -jet,e + E T miss (p  can also be derived)

13. EPS03 Meeting, 17 July 2003, Aachen 13 A/H  and A/H  at LHC, S.Arcelli A/H ,  jet + L= 30 fb-1 MA=  130 GeV tan  = 45 K  =1 A/H ,  e L= 30 fb-1 MA=  130 GeV tan  = 45 K  =1 Signal in 30 fb -1 M A =130 GeV, tan  =30,   = 1 Significance>5 up to M A  150 GeV Comparable significance in  jet +, e Analysis efficiently differentiates A/H  and A/H  (A/H   ), separation depends on on ,  M   (GeV) L= 30 fb-1 Events/ 2 GeV

14. EPS03 Meeting, 17 July 2003, Aachen 14 A/H  and A/H  at LHC, S.Arcelli 5  bounds on   range from 0  depending on tan  95% C.L. exclusion limits for    1 can be set with very low integrated luminosities (< 10 fb -1 ) Range 10 -2 –1 in  explored with L=100 fb-1 About 10-100 better reach than current limits from g-2 data, ~10 times better than Tevatron Limits on  depend on the Model: M   (GeV)   

15. EPS03 Meeting, 17 July 2003, Aachen 15 A/H  and A/H  at LHC, S.Arcelli Conclusions Despite low BR~2x10 -4, A/H  is a quite powerful channel for the detection and the study of the MSSM heavy neutral Higgs bosons: ● Complements “golden channel” A/H  in A/H discovery. ● Allows for a precise measurement of Higgs mass and provides the unique possibility to directly measure the A/H natural width at high tan  ● May allow to disentangle all neutral Higgs states in regions where h,H,A are non-degenerate, possibility under investigation (“ Intense-Coupling Regime”, M A ~ 130 GeV, high tan , E.Boss, A.Djouadi, A.Nikitenko, hep-ph/0307079) Within the framework of 2HDM models, the search for A/H  decays at the LHC will allow to test Lepton Flavour Violation with a much better sensitivity compared to current constraints from muon g-2 data, and to the bounds achievable at the Tevatron in the same search channel. Many thanks to my colleagues in CMS and ATLAS for providing material and help in preparing this talk, in particular K.Assamagan, R.Kinnunen, S.Nikitenko, M.Vos