LHC Prospects on Higgs and physics beyond the

LHC Prospects on Higgs and physics beyond the Standard Model (SUSY) • Riccardo Ranieri • INFN and Università degli Studi di Firenze • on behalf of ATLAS and CMS Collaborations • • • DIS 2006 XIV International Workshop on Deep Inelastic Scattering • Tsukuba (Japan), 20 -24 April 2006

ATLAS & CMS at LHC – Detectors optimised for Higgs boson and SUSY searches § very high energy: LHC pp √s=14 Te. V – inelastic cross section: σpp=55 mb – interaction rate: 40 MHz § high luminosity: (2 x)1033 cm-2 s-1 1034 cm-2 s-1 CMS = Compact Muon Solenoid – per year: 20 fb-1 100 fb-1 § BIG detectors – CMS: 15 m x 21. 5 m – ATLAS: 25 m x 46 m LHC = Large Hadron Collider first collisions in Autumn 2007 DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics ATLAS = A Toroidal LHC Apparatu. S 2

LHC DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 3

ATLAS DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 4

CMS DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 5

Expected LHC schedule 1 st July 2007 LHC closed and set up for beams someday in 2008 first physics run (few fb– 1) August 2007 first beam in machine from 2009 October / November 2007 first collision followed by a short pilot run (~10 pb– 1) DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics physics run 10/20 fb– 1 to 100 fb– 1 per year M. Lamont @ Te. V 4 LHC, April 2005 http: //lhccommissioning. web. cern. ch/lhccommissioning/presentations/lamontcomm-tev 4 lhc. ppt 6

Where will we be at LHC startup? ¿ Higgs boson signal m. H=115 Ge. V/c 2 from LEP 2 data ? Searches at Te. Vatron up to LHC startup… û year 2007: ~2 fb-1 § m. H<125 Ge. V/c 2 covered to exclusion ü year 2008: ~4 fb-1 § m. H<130 Ge. V/c 2 covered to exclusion § 3σ evidence up to m. H=125 Ge. V/c 2 FERMILAB-PUB-03/320 E CERN-EP/2003 -011 LHWG Note/200201 2 @ 95% CL m. H>114. 4 Ge. V/c DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 7

SM Higgs Production at LHC § Gluon Fusion – the highest cross section § Vector Boson Fusion – two high-p. T forward jets § Associated production tt. H and bb. H – high-p. T lepton, top reconstruction, b-tag § Associated Production WH and ZH – one or two high-p. T leptons useful for the trigger DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 8

SM Higgs Decays LEP excluded 2 m. Z “light” Higgs – decays into Vector bosons W and Z – hadronic and decays are favourite » “golden” channels – two-photon decays » …but difficult to select DIS 2006 Tsukuba, 20 -24 April 2006 » extremely “clean” but rare and difficult to detect LHC Prospects on Higgs and BSM Physics 9

Low Mass Higgs: H→ This decay is very rare (Br≈10 -3) § σ(pp→H 115)x. Br(H→ )=76 fb (NLO) S/B≈1/20 – good resolution mass peak – Electromagnetic Calorimetres crucial for H→ : σ(m )/m ≈1% needed § motivation for LAr (ATLAS) and Pb. WO 4 (CMS) calorimetres – high granularity – response uniformity – 3 main background processes: CERN/LHCC 96 -40 ATLAS TDR 1 CERN/LHCC 96 -41 ATLAS TDR 2 DIS 2006 CERN/LHCC 97 -33 CMS TDR 4 Tsukuba, 20 -24 April 2006 » » irreducibile: gg/qq→ 81 pb +jet (with “real” or “fake” second photon) 9 x 104 pb hadronic QCD jets (π0 decays) 108 pb ATLAS reach with 10 fb-1 and m. H=115 Ge. V/c 2: » Signal Significance: S/√B=2. 0 (K-factors not included) 10 LHC Prospects on Higgs and BSM Physics

Low Mass Higgs: tt. H (→bb) This is the favourite decay § σ(pp→H 115)x. Br(H→bb)=28 pb S/B<10 -7 § tagging the top quarks helps a lot 1. t→b. W(→μν) 2. t→b. W(→jj) § “crowded” final state – 6 jets (4 of them are b-jets) + additional ISR/FSR jets » 4 b-tagged jets needed to reduce combinatorics – 1 isolated lepton » it’s the key for trigger § optimised analysis – – pzν from W-mass constraints likelihood pairing of jets DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics » Final result for likelihood analysis (m. H=115 Ge. V/c 2): » 30 fb-1: S/√B=3. 4 » 10 fb-1: S/√B=2. 0 ATL-PHYS-2003 -024 11

High mass Higgs: H→ZZ (*) → 4μ – The “golden” golden channel § well defined peaks Z→μ+μ– m. H>2 m. Z: real Z’s § main backgrounds – reducible: tt, Zbb » μ isolation » Z reconstruction (m. Z) – irreducible: ZZ » qq- production mechanism dominates softer muons § Luminosity required for a 5σ discovery: – 10 -30 fb-1 if m. H>2 m. Z » 2 -3 low luminosity LHC years – up to 100 fb-1 if m. H<2 m. Z » only one reconstructed Z » high luminosity runs DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics CMS AN 2003005 CMS AN 2003007 15

ATLAS & CMS Discovery Potential CERN/LHCC 99 -15 ATLAS TDR 15 CMS NOTE 2003/033 § After detector calibration and LHC pilot run… – …almost all the “allowed” mass range can be explored during the first year (10 fb-1) DIS 2006 Tsukuba, 20 -24 April 2006 –. . . after 2 years (≈30 fb-1) 7σ significance over the whole mass spectrum, covered by more than one channel LHC Prospects on Higgs and BSM Physics » LEP excess is near… 16

MSSM - m. SUGRA 5 Higgs bosons: 2 neutral CP-even: h, H 1 neutral CP-odd: A 2 charged: H+, H- 4 charged fermions: ± Charginos: ~1, 2 m. SUGRA 5 parameters: m½, m 0, tanβ, A 0, sign(μ) DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 4 neutral fermions: 0 Neutralinos: ~1, 2. 3, 4 17

MSSM Higgs boson masses Higgs Mass [Ge. V/c 2] Phys. Rev. D 66: 055004, 200 2 – Born level hep-ph/0205160 § § m h <m Z m A <m H m W < m H± m. A=(m. H± 2 -m. W 2)½ – Loop corrections § depend on top and stop masses, mixing, … § modify previous sequence, important for h m. H, m. A and m. H± degenerate for m. A>140 Ge. V/c 2 mh increases with m. A up to asymptote: mh<130 Ge. V/c 2 when m. A/m. Z>>1 MSSM h behaves as a SM Higgs DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 18

Neutral MSSM Higgs at LHC – Production: » » gg→A/H pp→A/Hbb – Neutral Higgs mixing (α) modifies couplings to bosons and fermions with respect to the Standard Model – high tanβ » enhanced decays h/H/A→bb, ττ – low mixing α » h→bb, ττ suppressed DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 19

H and A searches – Complete coverage of (m. A, tanβ) plane with 30 fb-1 – A lot of decay channels – “SM like” » high tanβ-m. A region is the more accessible » only h detectable in most of the plane » h→ , bb » H→ 4ℓ – purely MSSM » » A/H→μμ, ττ, bb H→hh A→Zh H±→τν, tb – if decay into SUSY sparticles are allowed » H/A→ ~ 20 ~02 ~0 ~0 » 2→h 1 95% CL Limits hep-ex/0602042 DIS 2006 Tsukuba, 20 -24 April 2006 (LHWG Note 2005001) mt=174. 3 Ge. V/c 2 mh [Ge. V/c 2] m. A [Ge. V/c 2] tanβ No mixing (2005) >93. 6 0. 4÷ 10. 2 mh max (2005) >92. 8 >93. 4 0. 7÷ 2. 0 LHC Prospects on Higgs and BSM Physics 20

h/H/A →μ+μ- § Enhancement of BR(h/A/H→μ+μ-) for high tanβ – Main backgrounds: » Drell-Yan Z/ *→μ+μ» tt (both t→b. W→bμνμ), Zbb – Background suppression » b-tagging (suppresses DY) » central jet veto (reduces tt, Zbb) » ETmiss cut (reduces tt) § Three regions (mh max<135 Ge. V/c 2): 1. Decoupling regime m. A>>mhmax » h similar to SM, A/H indistinguishable CMS AN 2005 -033 5σ 2. Low m. A regime m. A<mhmax » H similar to SM, h/A degenerate » Z peak, high luminosity needed 3. Intense coupling regime m. A≈mhmax » h/H/A not degenerate in mass » indistinguishable (detector resolution) DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics without systematic uncertainties 21

MSSM Charged Higgs § H± production – if m. H±<mt: t→H±b – if m. H±>mt: gb→t. H± § Decays: – if m. H±<mt: H±→τν – if m. H±>mt: H±→tb § LEP 95% CL limit: – m. H±>78. 6 Ge. V/c 2 » decay channels: H±→τν, cs LHWG Note 2001 -005 hep-ex/0107031 DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 23

H± searches CMS NOTE 2000/039 CMS NOTE 2000/045 CMS NOTE 2002/024 CMS AN 2005 -067 CMS AN 2006 -028 § m H± < m t – search in tt events » lepton from top quark » τ from H±→τντ – excess of τ’s in tt events » H± mass can not be reconstructed § m H± > m t – associated production with top » gb→t. H±(→τντ, tb) – background from tt and Wt » final states with τ leptons DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 24

SUSY LHC discovery reach § 1 fb-1 of data should allow discovery if squark or gluino mass < 1. 5 Te. V/c 2. § ATLAS and CMS potentials similar ~ g (1 Te. V/c 2) § Those studies assumed a perfectly known SM physics (only statistical errors on background rate) and ideal detectors (perfectly ~ q (1 Te. V/c 2) aligned, nominal asymptotic performance) § SUSY discovery likely to depend not on statistics but on the understanding of SM background and detector systematics: excess of events DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 1 fb-1 25

It is not enough to observe the excess over the Standard Model… DISCOVERY SUSY SPECTROSCOPY This requires a different approach… Fix a set of points in the parameter space Get information on the spectrum (end-points) Reconstruct sparticles DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 27

The golden decay § The neutralino leptonic decay is the starting point for reconstruction of the sparticle masses CERN/LHCC 99 -14 ATLAS TDR 14 p p CERN/LHCC 99 -15 ATLAS TDR 15 hep-ph/0007009 e+ e- q + m+ m∫L=30 fb-1 tanβ=2. 1 ~ g q~ q m 0=100 Ge. V/c 2 m½=300 Ge. V/c 2 A 0=-300 Ge. V sign(μ)=+ The measurement of the missing transverse energy ETmiss is the key point ~ c 02 ~ c 01 ~ l l l ∫L=5 fb-1 tanβ=6. 0 Edge accuracy with 30 fb-1: 0. 5% Mll (Ge. V/c 2) DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 28

Sparticle reconstruction p p 300 fb-1 b b – Lepton scale: – Reconstruction can be done with only 1 -10 fb-1 – Statistical uncertainties <<1% with 300 fb-1 – Main uncertainty: energy scale and LSP mass DIS 2006 Tsukuba, 20 -24 April 2006 » LHC goal: 0. 1% » material budget, alignment, magnetic field – Jet energy scale: » LHC goal: 1% » FSR, jet cone LHC Prospects on Higgs and BSM Physics 29

The earliest discovery? § A new resonance decays into two leptons… Z′ (new gauge boson) ? …? AH, ZH (Little Higgs) ? G(KK) (ADD) ? G(1) (Randall-Sundrum) ? DIS 2006 Tsukuba, 20 -24 April 2006 (1)/Z(1) (Te. V-1 Extra Dimensions) ? LHC Prospects on Higgs and BSM Physics 30

Conclusion – LHC has potential for Higgs boson(s) and SUSY particles discovery already in the first year (months? ) of operation § 1 LHC day at 1033 cm-2 s-1 ≡ 10 years at previous machines BUT – At the beginning a lot of time (whole first year? ) will be needed to understand the detectors, reach the desired performance, optimize physics selection and precisely measure SM backgrounds HOWEVER – The ATLAS and CMS detectors are designed for new physics searches, no surprise that they can cover most of the spectrum of Higgs and sparticle masses within 1 year of start of physics collisions DIS 2006 Tsukuba, 20 -24 April 2006 LHC Prospects on Higgs and BSM Physics 31