ckm2006 at nagoya university dec. 14 th 2006 makoto tomoto nagoya university on behalf of cms and...

CKM2006 at Nagoya University

Dec. 14th 2006 Makoto Tomoto Nagoya University

on behalf of CMS and ATLAS collaborations

Rare B decays in ATLAS and CMS

http://www.nagoya-u.ac.jp/en/

http://ckm2006.hepl.phys.nagoya-u.ac.jp/logo.htm

Makoto Tomoto (Nagoya University) CKM2006 at Nagoya

Outline

B physics in ATLAS and CMSATLAS and CMS detectors

BbXs

Conclusion


B physics in ATLAS and CMS• ATLAS and CMS

– p-p collision at s = 14TeV• (bb) = 500 b

– BdBd : B+B- : BsBs : b-barions = 4:4:1:1– 105 bb pairs/s @ L=1033 cm-2s-1

• “B-factory” as well as “New particle-factory”

• Detector design is dedicated to high-pT physics– Majority of B-events is low-pT

particles• Trigger and analysis are a challeng

e B-decays to ’s are promising• Strategy on B-physics in ATLAS and CMS

– CP violation (Low luminosity run)– Bs oscillation (Low luminosity run)– Rare B decay (Even in High lumi.) (BBK*, b)


• B and bsll– Sensitive to new physics

• SUSY etc.– FCNC transition

• Forbidden at tree diagram

– SM: Br(bsll) ~ 10-6 ~ 10-7

– |Vts| and |Vtd| determination– Wilson coefficient C7, C9, C10

Bsll

Bs

Br(B) Bs Bd

SM 3.510-9 0.910-10

CDF (780 pb-

1)1.010-7 95%CL

3.010-7

95%CL

DØ (700 pb-1) 2.010-7 95%CL

11.110-7

95%CL

Belle 78 fb-1 - 1.610-7 90% CL

BaBar 111 fb-1 - 0.610-7 90% CL

tan=50

10-9

10-8

Bd

Bs

Belle : 1.33+0.42-0.37 ±0.10 x 10-6

Br(BdK*) measurements

Babar : 0.86 ±0.16 x 10-6+0.79-0.58

Rare B decays


LHC

ATLASCMS

• 27Km ring, proton-proton collider, s=14TeV

• 4 experiments in LHC LHCb dedicated B-physics ALICE dedicated heavy ion Two general purpose detectors: CMS and ATLAS

• Operation plan - End of 2007: 900 GeV commissioning run

- After summer 2008: 14TeV, Low luminosity run (L = 1033cm-2s-1)

- Design: 14TeV, High luminosity run (L = 1034cm-2s-1)

LHC 27Km tunnel


Detectors

Compact Muon Solenoid

A Toroidal LHC ApparatuS

Total weight : 12500 TOverall diameter : 15.0 m Overall length : 21.5 mMagnetic Field : 4 Tesla

Total weight : 7000 TOverall diameter : 22.0 m Overall length : 46.0 mMagnetic Field : 2 Tesla (solenoid) 0.5 Tesla (toroid)


Inner Detectors

To reconstruct vertex of B decays Used in HLT, better b-ID Impact parameter significance Di muon mass resolution

ATLAS:Pixel, SCT, TRT in 2 T solenoid field

CMS: Pixel, Silicon tracker in 4 T solenoid field


pT- range for muons form B

IP resolution for ATLAS Final detector

CMS ATLAS

< 0.25

Tracker PerformanceImpact parameter M Mass Resolution

CMS

ATLAS

CMS pT>3-6GeV 50-90m

=36MeV(4Tesla)

=84MeV(2Tesla)

All

||<0.7

||>1.2

ATLAS pT>6GeV 25-70m

|| ||


Muon detectors

For trigger and offline selection to get pure rare B-decay samples

ATLAS:• RPC (barrel) and TGC (endcap) for LVL1 trigger• CSC and MDT for precise tracking in 0.5 T toroid field

CMS:• RPC (barrel) for LVL1 trigger• CSC and DT for precise tracking in 2 T solenoid field


Muon detectors

ATLAS Barrel muon

ATLAS Endcap muonCMS Endcap muon

CMS Barrel muon

ATLAS CMSCosmic ray run with real muon detectors!


ATLAS/CMS Trigger System

<2.5 s

~10 ms

~1 s

HL

T

~1-2 kHz out

~100 Hz out

Hardware

Software

40MHz

~100kHz

~150Hz

For rare B-decays, di-muon trigger is used

Region of Interest (RoI ):HLT reconstruct b-decays using partial reconstructionin RoI around L1 muon


20GeV

6GeV

ATLAS LVL1:

Requiring di-(6GeV),rate ~500Hz

ATLAS LVL2:Confirm each m RoI from LVL1Mass cut B : 4 GeV < M()< 6 GeV

ATLAS EF: Refit ID tracks in Level-2 RoIDecay vertex reconstructionTransverse Decay length cut:Lxy > 200m

di-muon trigger

pT>3GeV

1/2

singledirate ~900Hz

pT (GeV)CMS HLT:Primary vertex reconstruction - use three most probable verticesRegional track reconstruction - partial reconstruction with ≤ 6hits - Pt > 4 GeV Track pairs - mass windows for signal - (un)like sign chargeVertex fit - 2 <20 & Decay flight length > 150m

CMS LVL1:

LVL1: 2 RoI pT () >

6GeV (~500 Hz @ L=1033cm-2s-

1)

ATLAS

Online di- mass, (MeV)

B K* +

-

B+ -Not normalized


CMS offline analysis : B

2

COS

isolation

lxy/xy

After selections … 6.1 events/10fb-1 v.s. X background 13.8 +22.0 -13.8

lxy

pT(Bs)


ATLAS offline analysis : Bs

• pT>6GeV, ΔR<0.9• M = MBs

+140-70 MeV

• isolation: no charged tracks with pT > 0.8 GeV in cone < 15 degrees

• vertex fit with pointing to primary vertex constraint

• transverse decay length Lxy/(Lxy) > 11

B0s

signalBG (bbX)

pT>6 GeV, ΔR<0.9 50 events

6.0×106 events

Mcut 0.77 2×10-2

Isolation cut 0.36 5×10-2

Lxy/>11, 2<15 0.4 < 0.7×10-4

All cuts 7 20±20

Exected signal v.s. inclusive bbX bkgL=10fb-1(can be collected in a year)Br(Bs) = 3.5x10-9


Projected upper limits : Bs

totalBs

bgs

nnNBBr

L2

,0

7 signals and 20 backgrounds can expect upper limit on Br(Bs)

• Single experiment expects to reach the sensitivity of SM prediction

3 years of data taking : L=30fb-1

Still factor of ~10 aboveBoth ATLAS and CMS has proven to continue measurement of Bs at nominal LHC luminosity 1034 cm-2s-1. This will mean 100 fb-1 just in one year.

Tevatron projection

ATLAS/CMS expectation


Specific background study : Bs

Nu

mb

er o

f ev

ents

Fake events from

B0d→π -μ+νμ

B0s →µ+ µ-

Nu

mb

er o

f ev

ents

Mµµ Mµµ

B+l

BG process Br Effective Br in Bμμ signal reg

ion

B0 → π - µ+ νµ ~10-4 ~ 5 ∙ 10-8

B+ → µ+µ- ℓ+νℓ < 5 ∙10-6

< 5 ∙10-8

Bc → µ+µ- ℓ+νℓ < 10-4 < 10-8

B0d → π0 µ+µ- ~ 2 10∙

-8~ 10-10

B0s →µ+ µ- γ ~ 2 10∙

-8~ 10-10

Bd → Kπ Bs →KK 2 ∙ 10-5 < 10-9

B0d →µ+ µ-

Much high branching ratiocompared to Br(Bs)=10-9

Taking into account1. /K fake rate ~ 0.1-0.5%2. soft phase space ~ 10%

Generator level study

Needs further study with full simulation


bXs

experimetal points <AFB> simulated events with SM simulated events with positive MSSM C7

eff

BR used in the MC

Signature after trigger + offline reconstruction 30 fb-1

Models used in MC or to confront experimental sensitivities.

Signal Bkg

1.3 10-6

3.5 10-7

1.0 10-6

2.0 10-6

Bd→K0*

B+ →

Bs →

Br.fraction-massAFB

25001500 900

<50000

<10000

<10000

Melikhov, Nikitin, Simula, PRD57,98; Melikhov, Stech, PRD62, 2000 WC: SM Buras, Munz, PRD52, 95;MSSM Cho, Misiak,Wyller, PRD54,96.

b→ 800 < 4000 NP: Chen, Geng, PRD64,2001 Aliev NPB649,2003

ATLAS statistical error<5%b mass

= 25% = 21.5 MeV

Mass (MeV)

M. Biglietti et al. (ATLAS Coll.) Nucl. Phys B 156 (2006)

B

Forward-backward Asymmetry (AFB)


Conclusion

• ATLAS and CMS sensitivity to rare B-decay is expected to reach the level of SM prediction after 3 years of data taking– bs and B promising for new physics– We will directly and indirectly be able to search for new physi

cs at the same place and time• At LHC nominal luminosity 1034cm-2s-1, ATLAS and CMS can mak

e a measurement of Bs-> branching ratio just after one year. • More study using full simulation/reconstruction is under way• The installation and commissioning of the detectors are in good

progress

• Everyone is waiting for the data taking …


Backup or Old slides

Makoto Tomoto (Nagoya University) CKM2006 at NagoyaBobeth et. al., PRD66 074021 (2002)

Rare B-decays

Bs Bd

SM 3.510-9 0.910-10

CDF (780 pb-1) 1.010-7 95%CL 3.010-7 95%CL

DØ (700 pb-1) 2.010-7 95%CL 11.110-7

95%CL

Belle 78 fb-1 - 1.610-7 90% CL

BaBar 111 fb-1 - 0.610-7 90% CL

Bs

FCNC transition Forbidden at tree level Br(bsll) ~ 10-6 ~ 10-7

Br(B) ~ 10-9 ~ 10-10

Indirect search for new physics SUSY, Higgs etcFor bs transitions |Vts| and |Vtd| determination Wilson coefficient C7, C9, C10

tan=50

Bsll

10-9

10-8

Belle : 1.33+0.42-0.37±0.10 x 10-6

Br(BdK*)

Babar : 0.86 ±0.16 x 10-6+0.79-0.58

Bd

Bs

ckm2006 at nagoya university dec. 14 th 2006 makoto tomoto nagoya university on behalf of cms and...

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