What do we expect from LHC(b)? Tatsuya Nakada CERN and University - PowerPoint PPT Presentation

What do we expect from LHC(b)? Tatsuya Nakada CERN and University of Lausanne 19-23.2.2001, Ise, Japan

LHC Baseline pp Experiments

LHC magnet string

LHC prototype low- β quadrupole at KEK

LHC Plan Beam injection and a sector test in 2005 Detector installation completed: January 2006 LHC beam commissioning: February-March 2006 First collisions and pilot run: April 2006 L = ~ 5×10 32 cm −2 s −1 ,for 4 weeks Start of physics run: August 2006 L = ~ 2×10 33 cm −2 s −1 , for 7 months

Experimental Conditions Cross sections (PYTHIA) σ total 100 mb σ inelastic 80 mb σ inelastic − σ diffractive 55 mb σ bb 500 µ b σ cc 1.5 mb Machine parameters 40 MHz f bunch crossing 10 33 cm −2 s −1 L (B physics ATLAS, CMS) 2×10 32 cm −2 s −1 L (LHCb) (design luminosity 10 34 cm −2 s −1 )

General purpose pp experiments CMS ATLAS | η | < 2.5 Central detector: ~ Pixel vertex detector Si strip tracker High resolution E cal H cal High resolution muon system High P T lepton triggers

ATLAS SC coil for Cryostat for toroidal magnet Liquid Argon E-cal

CMS PbWO 4 E-Cal Fe yoke

Dedicated B detector 2.1 < η < 5.3 Forward detector: Si mini-strip vertex detector Inner and Outer Tracker RICH detectors E-cal, H-cal Muon system High P T hadron and lepton triggers Detached vertex trigger Dipole magnet

LHCb Hybrid Photo-Deitector straw driftchamber HPD pixel readout chip

LHCb Technical Designed Reports January 2000, submission September 2000, submission September 2000, submission April 2000, approved February 2001, approved February 2000, approved CERN/LHCC/2000-0037 LHCb TDR 3 7 September 2000 TDR Technical Design Report yoke, coil construction will construction will being orders start in 2001 start ~end 2001

Important Issue I: Hadron ID Without With hardon PID hardon PID (ATLAS) (LHCb) B → π + π − LHCb

Important Issue II: Trigger Lepton trigger (and no hadron ID) -ATLAS, CMS- trigger and tag l − + X l − + X b-jet + X bB bB bB π + π − l + l − + X l + l − + X ρ + π − bb D ∗ π : B + h + l + l − + X wrong (not very clean tag: > 0.4) ~ all Hadronic final states are not efficiently triggered.

Lepton+hadron trigger with hadron ID -LHCb- trigger and tag l − + X l − + X K − + X b-jet + X bB bB bB bB π + π − π + π − l + l − +X l + l − +X ρ + π − ρ ± π m D ∗ π D ∗ π ± K − + X bb : : B + h + bB l + l − + X l + l − +X (not very clean tag) Trigger efficiencies for the hadronic final states are very much enhanced. High tagging efficiency with good quality.

ATLAS and CMS Central geometry and no vertex trigger → high threshold values for the P T trigger (~6 GeV) = Low b efficiency LHCb Forward geometry and with vertex trigger → moderate threshold values for the P T trigger (1~2 GeV) = Higher b efficiency

LHCb Trigger Level-0 Hadron Level-1 Β→π + π − Working point stability

Difference can be seen by… B d → π + π − + tag ATLAS CMS LHCb σ m [MeV/ c 2 ] 70 27 17 Annual yield 2.3k 0.9k 4.9k B s → J/ ψ φ ATLAS CMS LHCb σ τ [fs] 63 63 31

LHC contributions to CP violation Improvement in statistics useful B sample @ LHC in one year > ~ Σ all previous B experiments by then Σ Σ Σ B d → J/ ψ K S (ATLAS, CMS, LHCb) σ (sin 2β ) < 0.01 B d → K ∗ µ + µ − (ATLAS, CMS, LHCb) 45k events/year LHCb B d → π + π − (LHCb, ATLAS??? ) ~5k flavour tagged/year B d → ρπ (LHCb) 100 flavour tagged ρ 0 π 0 /year ( Br = 10 −6 ) B d → D ∗ π (LHCb) 340k flavour tagged D ∗ π /year B d → K ± π m (LHCb) B d → φ K S (LHCb) Up to one π 0 in the final state.

B d → J/ ψ K S ATLAS CMS B d → ρ + π − LHCb

New decay modes Combination gives a B s → J/ ψ φ (ATLAS, CMS, LHCb) model independent value of arg V ub even with presence B s → D s K m (LHCb) ± of new physics. σ φ3 < 10° in one year. B s → K + K − (LHCb) B s → K ± π m (LHCb) | V ub | will be well known from the B factory experiments by then. B s → φ φ (LHCb) ( ρ , η ) With LHCb in operation, a model independent determination of the CKM parameters is possible even in a presence of New Physics . Effect due to new physics can be isolated unambiguously !!

Standard Model FCNC New Physics FCNC b d,s b d,s B d,s -B d,s + W W oscillations b d,s b d,s b → s,d penguin decays W No New Physics contribution to the Standard Model tree induced decay modes.

In addition... very rare decays Br < 10 −8 In one year with B s → µ + µ − , ATLAS CMS LHCb Br = 3.5×10 −9 Signal 9 7 11 L = 10 33 (ATLAS,CMS) Background 31 1 3.3 2×10 32 ( LHCb) forbidden in the Standard Model B s → e ± µ m , B d → e ± µ m , τ ± → µ ± µ ± µ m LHCb (very preliminary): τ ± → µ ± µ ± µ m upper limit of < 1.8×10 −7 @ 90% CL in one year @ L = 2×10 32 Possible improvements for LHCb Running with higher luminosity: 5×10 32 Dedicated trigger combinations: Two or three high P T muons with a relaxed requirement on the detached vertex.