FPCP 2003 : 3-6 June 2003 Ecole Polytechnique, Paris Status and Prospects of ATLAS and CMS for B...

FPCP 2003 : 3-6 June 2003 Ecole Polytechnique, Paris

Status and Prospects of ATLAS and CMS for B Physics and CP Violation

Fairouz Ohlsson-MalekLPSC-Grenoble/IN2P3/ATLAS 1

Status and Prospects of ATLAS and CMS

for B Physics and CP Violation

Overview of the Detector Status Overview of the physics potential B physics reach:

•Trigger,Tagging and off-line strategies•Precision physics•Physics of Bs meson•Potential for rare decays•B hadron production

Conclusions




LHC reach

• high detector granularity large event size (O(1) MByte)

• high collision rate (~ 108 – 109 per sec )

Collision Energy 14 TeV

Design Luminosity

1034 cm-2 s-1

Interactions per Bunch Crossing

23

Bunch spacing 25 ns

B-meson decays, precise measurementsB-meson decays, precise measurements•CP violation CP violation •BBss mesons mesons•Rare decaysRare decaysB-hadron production B-hadron production •Double heavy flavor mesons Double heavy flavor mesons •QCD tests of beauty production at LHC QCD tests of beauty production at LHC central regioncentral region•Physics of Beauty baryons, production Physics of Beauty baryons, production polarizationpolarization




100b

230b

LHC

total= 100 mb

inelastic = 80 mb

bb = 500 b

ATLAS & CMS

Central detectors

LHCb

Forward detector

|| < 2.5 , pT> 10 GeV

B-hadron = 100 b

1.9 < < 4.9, pT>2 GeV

B-hadron = 230 b

L = 1-2 x 1033 cm-2 s-1

1034 cm-2 s-1 for rare decays

L = 2 x 1032 cm-2 s-1

Exclusive channels ~ 2.8 106

Dominated by bb J/Hadronic channels: < 105

(however all with muon tag)

Exclusive channels ~ 3.4 106

1.7 106 bb J/Hadronic channels ~ 1.7 106

Overview of the B physics potential




Trigger Strategies

ATLAS CMSLevel 1 1 pT> 6 GeV, ||

<2.4

26 GeV

1 pT> 14 GeV, || <2.4

23 GeV

Level 2 Lepton reconstruction and Identification

Track reconstruction either in full ID volume or in ROI followed by mass cuts on track combinations

Event Filter

Offline algorithms, Decay vertices cuts ….




Trigger Strategies

2 trigger:LVL1: 2 , LVL2: track in spectrometer+InnerBd J/ () Ks, Bs J/() ,b J/ () , B , B K*0 , B

-e() trigger:LVL1: eGeV, LVL2: tracking in regionBd J/ (ee) Ks + B b J/ (ee) + B d…-hadron trigger:LVL1: + jet (ET> 5 GeV), LVL2 tracking in regionB + B , Bs Ds + B , ….

ATLAS as an example




B Tagging strategies

l

B0

B0D

K-

b

b

d

u

d

u

B0

+

Opposite side lepton tag:

ATLAS CMS

Efficiency 4% (e+) 4%

D 0.52(), 0.46 e 0.44

ATLAS CMS

Efficiency 82% () 21%

D 0.16() 0.32

Same side pion (B** + fragmentation):

ATLAS CMS

Efficiency 64% () 65%

D 0.17() 0.18

Jet charge – same (ATLAS) and opposite (CMS) side:




Precision measurements

Benchmark channels:Bd J/ Ks sin2 Bd +- sensitivityBsJ/ weak phase s, s BsDs (a1) ms B+ K+ K+ - Br

Upper limit on Br= 5.3 10-7 for 3 years @ 1033 cm-2 s-1




Precision measurements

1 year @ 1033 cm-2 s-1 ATLAS CMS

N Triggered events

N Offline events

S/B

800 000 ev

170 000 ev

31

4400 000 ev

430 000 ev

8

sin2

Lepton tags

Jet/charge tags

Total

0.039

0.026

0.017

0.031

0.021

0.015

ATLAS+CMS

3 years @ 1033 cm-2 s-1

ATLAS+CMS

3 years @ 1033 cm-2 s-1

+ LHCb, 5 years @ 1032 cm-2 s-1

0.007 0.005

The case of Bd J/ Ks sin2

Systematics can be controlled with very high statistics using control samples such as B+ J/ K+




Physics of Bs mesonsCP violation weak phase s= 2= 22

Bs oscillation parameterms

Precision ons ~ 8-12%, s

Benchmark channels:Bs J/ Bs Ds Bs Ds a1

ATLAS CMS

Proper time resolution

51 fs (60%)

107 fs (40%)

70 fs

ms 5 meas. up to

36 ps-1 30 ps-1

Measurable values up to ms

22.5 ps-1 26 ps-1

1 year @ 1033 cm-2 s-1




Physics of Bs mesonsBs J/

BR(BsJ/ )=(9.3±3.3)x10-4

J/ℓ+ℓ- (BR≈6%), K+K (BR≈49%)

HLT mass resolutions HLT mass resolutions

= 22.4 = 22.4 MeVMeV

= 2.2 = 2.2 MeVMeV

= 46.5 = 46.5 MeVMeV

J/J/ BBss

CMS studies

Lvl-1 Lvl-1 Lvl-2 Lvl-2 Lvl-2 Rate Lvl-2 Rate Lvl-3 Lvl-3 Lvl-3 RateLvl-3 Rate Events/ 10fbEvents/ 10fb-1-1

16.5%16.5% 13.7%13.7% 14.5 Hz14.5 Hz 8.7%8.7% <1.7Hz<1.7Hz 8380083800




Physics of Bs mesons

Benchmark channels:Bs J/ Bs J/

s= 2= 22SM predicts s ~O(0.03) New Physics

S/B >~1.

.30,33.0)(sin

.19,17.0)(sin

sM

sM

x

x

models some in %40 toup and %10 BSMCP

SMCP aa

Experimental lower limit

Theory:

ATLAS studies

Bs J/




Potential for studying rare decays

FCNC bs or bd only at loop-level in SM Br < O(10-5)

B K* , B , B , B K* , ….

b s,d

W-

u,c,t

b s,d

?

Sensitive to new physics:New diagrams appearing :charged Higgs, chargino, squark contributions|Vtd| |Vts| in SMComplementary determination from ms




Potential for studying rare decaysThe case of B K*

B K*

ATLAS 1995

CMS 4200

5% precision on AFB after 3 years @ low lumi

)cos(

0

1 )cos()cos(

1

0 )cos(

1)(

22

ddsd

dd

dsd

d

dsdsAFB

SM

MSSM C7 >0

MSSM C7 <0

Three points: mean values of AFB in three q2/MB

2 experimental regions with error bars




Potential for studying rare decaysThe case of B

Mass resolution Mass resolution

HLTHLTFull Full

TrackerTracker

= 46 = 46 MeVMeV

= 74 = 74 MeVMeV

CMS studies for Bs

Offline analysis results Offline analysis results (hep-ph/9907256), (hep-ph/9907256), using SM BR=using SM BR=3.5x103.5x10-9-9

(Lvl-1 trigger in |(Lvl-1 trigger in ||<2.4 |<2.4 instead of |instead of ||< 2.1)|< 2.1)10 fb10 fb-1 -1 => 7 signal events => 7 signal events with <1 backgroundwith <1 background 55 observation with 30 fb observation with 30 fb-1-1

and analysis could be and analysis could be perfomed perfomed at high lumi tooat high lumi too

Bs Bd Background

ATLAS 92 14 660

CMS 26 4.1 < 6.4

1 year @1034 cm-2 s-1




Potential for studying rare decaysexploring more difficult modes: Bd K*

ATLAS studies

S

B~ 19

Level 1: 6

Level 2: cluster candidate is selected if

Cluster Et > 4 GeV

0.5 strips cluster width 3.5 strips

Energy leakage in direction 9 %

Energy leakage in direction 9 %

Energy proportion of strips 2nd maximum 6%

2nd maximum physical meaning 1.5%

Shower shape

/0 rejection

Very preliminary




B hadron production at LHC

QCD

Semihard

PYTHIA

CDF measurement of b-b correlation using - b-jet data and comparison to models

QCD - NLO describe the shape of differential cross section however underestimates absolute value of cross section by factor ~2.4

The case with Fermilab




B hadron production at LHC

ATLAS - proposal for measurement of b-b production correlations using exlusive B-decay and semi leptonic decay to muon:

B Bd J/Ks0, B Bs J/

No degradation of efficiency as b-b close in space.

=J/ -




Conclusions

General purpose central LHC detectors ATLAS and CMS are well equipped for multi thematic B-physics program - including B-decays and B-production.

1. In CP violation the main emphasis will be on underlying mechanisms and evidence of New physics. ATLAS and CMS are especially precise in measurement of . LHC ‘gold-plated’ mode is also Bs J/

2. Bs mixing studies make clear that there is sensitivity to ms far beyond SM expectations. The width difference s can be measured best in Bs J/ with relative precision 8%.

3. Rare decays B have the most favorable experimental signature allowing to measure also at nominal LHC luminosity 1034 cm-2 s-1. Will measure branching ration of Bs which is in SM of order Br<(10-9). Precision measurements will be done for B K*.

4. Beauty production and correlations at central LHC collisions will be measured for QCD tests. The program includes baryon production polarization

5. ATLAS and CMS beauty trigger strategies will be adapted according to luminosity conditions at initial LHC period.

FPCP 2003 : 3-6 June 2003 Ecole Polytechnique, Paris Status and Prospects of ATLAS and CMS for B...

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Transcript of FPCP 2003 : 3-6 June 2003 Ecole Polytechnique, Paris Status and Prospects of ATLAS and CMS for B...