Flavor physics with CMS: Status and Perspectives · 2 KK mass (GeV/c 1 1.02 1.04 1.06 1.08 1.1 1.12...

Flavor physics with CMS:Status and Perspectives

Urs Langenegger(PSI)

Flavor Physics and CP Violation 20102010/05/25

• Introduction

• Data results at√s = 7TeV

. tracks and muons

• Example Perspectives. B0

s → µ+µ−

. top

Heavy Flavor Physics in CMS

σ tot

σ

σ t t

(W )ν

σ Higgsm = 500 GeV

H

m = 175 GeVtop

1 mb

1 b

1 nb

1 pb

µ

0.1 1.0 10 100

s TeV

σ

σb b

(pro

ton

- pr

oton

)

0.001 0.01

CERNFermilab

LHC

UA1

E710

UA4/5

UA1/2

CDF, D0

(p p)

(p p)

CDF, D0(p p)

σ •BRγγ : mH=100 GeVMAX

σ •BR4l : mH=180 GeVSM

—>

—>

—>

GHz

MHz

kHz

Hz

mHz

event rate

= 10 cm sec 34 -2 -1

event / year

1016

1014

1012

1010

108

106

104

102

L1input

HLTinput

HLT output

40 MHz

30-100 kHz

100 Hz

• Beauty and top quark physics. production: QCD (and EW). decays: FP(CP). Search for ‘New Physics’

. indirectly: b, t decays

. directly: t production

• Motivations. interesting physics:

SM rediscovery and measurementsBSM searches

. abundant signals from the start

. commissioningdetectortriggerdata management

. essential background determinationfor many other searches

Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 2

Continuous Evolving Program

[pb ]−1

0.1 1 10 100 103 104 105 106 107

ExclDsignals

J/ψ: prod

./pola

rization

Incl b

and Υ

(nS)

ExclB

bbcorre

lation

s

UL(B

0s→µ+ µ− )

excl.B0sdecays

Λ b→Λµ+ µ− , e

tc

B(B0s→µ+ µ− )

B(B0 →

µ+ µ− )

tt production

singlet production

R=

Γ(t→bW

)

Γ(t→qW

)

UL(X→tt)

UL(t→qγ)

UL(t→qZ)

c/b physics

top physics

• Reminder:. 2010: roughly 100 pb−1 of delivered integrated luminosity at

√s = 7TeV

. 2011: roughly 1 fb−1 at√s = 7TeV

. 1034 cm−2s−1: roughly 30 fb−1 per year (at√s = 14TeV)

with many intermediate and/or improved results


The CMS Detector

C ompac t Muon S olenoid

Pixel Detector

Silicon Tracker

Very-forwardCalorimeter

ElectromagneticCalorimeter

HadronCalorimeter

Preshower

MuonDetectors

Superconducting Solenoid

JINST 3, S08004 (2008)

• Requirements. lepton ID. b/τ tagging. jets and ET/

(and affordable)

Component Characteristics resolutionsPixel 3/2 Si layers δz ≈ 20µm, δφ ≈ 10µmTracker 10/12 Si strips δ(p⊥)/p⊥ ≈ 1%ECAL PbWO4 δE/E ≈ 3%/

√E ⊕ 0.5%

HCAL (B) Brass/Sc, > 7.2λ δE/E ≈ 100√E%

HCAL (F) Fe/Quartz δ(ET/ ) ≈ 0.98pP

ETMagnet 4 T solenoidMuons DT/CSC + RPC δ(p⊥)/p⊥ ≈ 10% (STA)

Weight 12’500 tLength 21.6mDiameter 15mMagnetic field 4 TCost ‘500’MCHF


Muon Reconstruction

muon track

global muon track)

inner track

:

JINST 5, T03022 (2010)

• Redundant precise muon trajectory measurement. barrel: drift tubes (tracking) plus RPC (timing). endcap: cathode strip chambers (tracking) plus RPC (timing). inner tracker: silicon pixel and strip detectors

• Muons. standalone muon:

reconstructed in muon system only. global muon (‘GM’): outside-in

standalone muon→ to inner track. tracker muon (‘TM’): inside-out

inner track→ muon detector


Muon Trigger (at ‘high’ luminosity)JINST 5, T03022 (2010)

• Muon trigger. L1 trigger: DT/CSC/RPC. High-level trigger:

L2: improve L1 measurementL3: combine with inner tracker (in r.o.i.)

• L3 efficiency measured in 2008 cosmic muon data taking. OIHit: outside-in with tracker seeds. OIState: outside-in with L2 seeds. IOHit: inside-out (low efficiency b/c pixel r/o only 1bc; cosmics asynchronous)

• HLT thresholds:. double muon: 3GeV


Low-luminosity triggering• Beam monitoring detectors used for triggering at low luminosity

. beam scintillator counters• BSC1: located at ±10.9m inner radius 20 cm• BSC2: located at ±14.4m inner radius 4 cm• NIM electronics

. beam pickup timing detectors• measure mirror charges of passing beam (bunches)

• Other applications:. beam halo triggers. beam gas triggers. zero-bias triggers. minimum-bias triggers

• BSC to be replaced after run 1. radiation damage. essential for HI MB triggering


Data Taking

• Early April:. delay scans for many subdetectors

• Except for detector studies: data taking efficiency > 90%Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 8

Detector Performance Impressions

Number of Tracks0 10 20 30 40 50 60

Num

ber

of E

vent

s

0

2

4

6

8

10

12

14

16

310×CMS Preliminary

=900GeVs

DataSimulation

(GeV/c)T

p0 1 2 3 4 5 6 7 8 9 10

Num

ber

of T

rack

s / 0

.2 G

eV/c

1

10

210

310

410

510

610 CMS Preliminary

=900GeVs

DataSimulation

PV resolution

Pixel cluster chargeTrack multiplicity and p⊥ spectrum

CMS-PAS-TRK-10-001

• MC simulation. detector well

described. need for some

physics tuning


V0 reconstruction

)2 invariant mass (MeV/c-π+π420 440 460 480 500 520 540 560 580

2C

andi

date

s / 1

MeV

/c

0

200

400

600

800

1000

1200CMS Preliminary = 900 GeV and 2360 GeVs

DataSimulation

)2 (+ c.c.) invariant mass (MeV/c-πp1080 1100 1120 1140 1160 1180

2C

andi

date

s / 1

MeV

/c

0

100

200

300

400

500

600 CMS Preliminary = 900 GeV and 2360 GeVs

Data

Simulation

mPDG :497.61MeV

mPDG :1115.68MeV

CMS-PAS-TRK-10-001

• Long-lived particles (cτ > 1 cm). oppositely-charged tracks. detached from primary vertex. forming a good secondary vertex. Λ: high-momentum track = p

• Track requirements. Nhits > 5. χ2/dof < 5. dxy/σ(dxy) > 0.5

• Vertex requirements. χ2/dof < 7 and dxy/σ(dxy) > 15

• Both lifetimes consistent with PDGV0 Data [MeV] MC [MeV]

KS peak 497.68± 0.06 498.11± 0.01KS width 7.99± 0.14 7.63± 0.03Λ peak 1115.97± 0.06 1115.93± 0.02Λ width 3.01± 0.08 2.99± 0.03


More Baryons: Ξ−→ Λπ−, Ω−→ ΛK−

• Reconstruction of Λ(π,K). loose Λ selection

vertex dxy > 10σ

track d0 > 0.5σ

|mΛ −mPDGΛ | < 8MeV

. track selectiond3d

0 > 3σ wrt PV (w/o signal tracks)kaon p⊥ > 600MeVcharge correlation of meson tracks

. vertexingP (χ2) > 1%

dVtx > 4σ

. events with single candidates only

• Masses and widths. consistent with PDG and MC


Candidate decay Ξ+→ Λ(→ pπ+)π+


Particle identification: tracker dE/dx

)2KK mass (GeV/c1 1.02 1.04 1.06 1.08 1.1 1.12

)2C

and

idat

es /

( 0.

001

GeV

/c

0

100

200

300

400

500

600

700

Width fixed to PDG value

)2KK mass (GeV/c1 1.02 1.04 1.06 1.08 1.1 1.12

)2C

and

idat

es /

( 0.

001

GeV

/c

0

100

200

300

400

500

600

700

CMS preliminary = 900 GeVs

candidatesφ 102 ±1728

2 0.32) MeV/c±Sigma = (1.29

2 0.22) MeV/c±Mass = (1,019.58

deuterons

CMS-PAS-TRK-10-001

• Measure specific ionization energy loss. analog readout of silicon strip detector. high purity tracks, Nhits > 9. robust dE/dx estimatorIh =

( 1N

∑i cki

)1/k, k = −2

• Inclusive reconstruction of φ→ K+K−

. Tracks: p > 1GeV or |m−mK| < 200MeV


Inclusive Reconstruction of D0

[GeV]πK m1.7 1.75 1.8 1.85 1.9 1.95 2

Can

dida

tes/

0.1G

eV50

100

150

200

250

300CMS preliminary

= 7 TeVs

0.002 GeV±: 1.867 µ 0.002 GeV±: 0.016 σ

45±N: 493 : 13.1S+BS/

• Dataset: 27 million minimum bias events

• Decay mode reconstruction

D0 → K−π+

• Selection criteria. transverse momentum cuts

p⊥(K) > 1.25GeV

p⊥(π) > 1.0GeV

p⊥(D0) > 3.0GeV

. Vertexing cutsd(K,π) < 0.025 cm

χ2

< 4.5

3 < lxy/σ(lxy) < 20

σ(lxy) < 0.03 cm

. D0 momentum vs. PV-SV direction∠(~p

D0, PV : SV ) < 0.1

. allow for multiple candidates

• MC expectations. Peak: 1.863± 0.002GeV. Width: 0.014± 0.002GeV


More Open Charm: D∗+

• Data set: 37 million minimum bias events

• Decay mode reconstruction

D∗+ → D0π+s → K−π+π+

s

• Kinematic selection

p⊥track > 0.6GeVp⊥

πs > 0.25GeV

p⊥D∗+ > 5GeV

choose single D∗+ candidate(with highest transverse momentum)

• Mass windows (for other projections)

|mKπ −mD0

PDG| < 25MeV

|mKππs −mKπ − δmPDG| < 1.2MeV


. . . and D+

• Data set: ≈ 11 million minimum bias events

• Decay mode:

D+ → K−π+π+

• Kinematic selection. p⊥ > 0.1GeV. p > 1GeV

• Vertexing selection. ~pD+ should point to PV (5σ). PV: P (χ2) > 0.01. SV: P (χ2) > 0.02. L/δ(L) > 7

• Note: D0 vs. D∗+ vs. D+

. three independent analyses

. unified selection was not a goal


Charmonium

GM+GM

GM+TM

see poster by M. Musich!

• This is not really flavor physics. but important ingredient and milestone

• Dataset: ≈ 1 nb−1, single muon trigger. p⊥ > 3GeV (rate limited at some point)

• Reconstruction of J/ψ → µ+µ−

. track selectionNhit > 10

d0 < 5 cm, dz < 20 cm

. vertex selectionP (χ2) > 0.1%

• YieldsCategory Yield Mass [MeV ] Width [MeV ]

GM+GM 24± 5 3094± 9 35.5± 6.8GM+TM 76± 12 3095± 7 42.5± 6.3

• Mass resolution. strongly pseudorapidity dependent

. average ≈ 30MeV with ‘100 pb−1 alignment’Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 17

B0s → µ+µ−: Search for New Physics

+l

−l

+H

h , ...0

H ,0

Z ,0b

s(d)t

t

W ,+

b

−l

+l

~lt,c,u

−W , χ0

χ0

~d

~

~+W ,

s(d)

ν

• Decays highly suppressed in Standard Model (Artuso et al, 2008)

. effective FCNC, helicity suppression

. SM expectation:

B(B0s → µ

+µ−) = (3.86± 0.15)× 10−9

B(B0 → µ+µ−) = (1.06± 0.04)× 10−10

. Cabibbo-enhancement (|Vts| > |Vtd|)of B0

s → µ+µ− over B0 → µ+µ−

only in MFV models

• Sensitivity to new physics. 2HDM: B ∝ (tanβ)4,mH+; MSSM: B ∝ (tanβ)6

→ Constraints on parameter regions→ ‘Measurement’ of tanβ (Kane, et al. ph/0310042)

• Plus: ‘time-dependent’ physics program. very early data: π,K muon misid rates with b→ µD0(K−π+)X. early data: B+ → J/ψK+, B0

s → J/ψφ normalization/control sample. some more data: B(B0

s → µ+µ−) upper limit. even more data: B(B0

s → µ+µ−) measurementUrs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 18

B0s → µ+µ−: Analysis Overview

µ

µ

b

b_

• b-hadrons produced in. gluon splitting (close together). flavor excitation. gluon-gluon fusion (back-to-back)

• Signal signature. two muons from one decay vertex and not much else in vicinity. dimuon mass around mB0

s

• Background composition. two independent semileptonic B decays (mostly from gluon splitting). one semileptonic (B) decay and one misidentified hadron. rare single B decays (peaking and non-peaking)→ roughly similarly importantno prompt+cascade muons from one single B decay (within current BG MC statistics)

⇒ High signal efficiency and high background reduction. one decay vertex and large/significant flight length. isolation of dimuon system. mass window, sidebands for non-peaking background estimation


MC simulations: B0s → µ+µ−

3Dσ/3Dl0 10 20 30 40 50

even

ts/b

in

−210

−110CMS preliminary

SignalBackground

xyαcos 0.97 0.975 0.98 0.985 0.99 0.995 1

even

ts/b

in

−310

−210

−110

CMS preliminarySignalBackground

/ndof2χ0 5 10 15 20

even

ts/b

in

−310

−210

−110CMS preliminary

SignalBackground

I

0 0.2 0.4 0.6 0.8 1

even

ts/b

in

00.020.04

0.060.08

0.10.12

0.140.16

0.180.2

0.22CMS preliminary

SignalBackground

[GeV]µµm4.8 5 5.2 5.4 5.6 5.8 6

even

ts/b

in

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6CMS preliminary

σ = 53.0± 1.4MeV

CMS-PAS-BPH-07-001

• Muon selection. 2 global muons (GM). p⊥ > 4GeV, |η| < 2.4

• B0s candidate. p⊥ > 5GeV, |η| < 2.4. 4.8 < mµ+µ− < 6.0GeV. Secondary vertex fit• cos(α) > 0.9985 (i.e. 3.1)• l3D/σ3D > 17.0

• χ2 < 5.0

. Isolation

I =p⊥(B0

s)

p⊥(B0s) +

Ptrk |p⊥|

> 0.850

using tracks withp⊥ > 0.9GeV and ∆R(t, B0

s) < 1


B0s → µ+µ−: Expected Performance

normalized to ‘nominal’ years:

CMS-PAS-BPH-07-001

Signal yield

Signal efficiency

BG rejection

BG: dimuons

BG: muon+fake

BG: rare

• With 1.0 fb−1 at√s = 14TeV, expect to obtain at 90% C.L.

nS = 2.36+0.076−0.074(stat)

εS = 0.023± 0.001(stat)

εB = (7.82± 0.369)× 10−9

(stat)

nµµB = 2.54

+0.719−0.560(stat)

nµhB = 2.54

+0.719−0.560(stat)

nnon−rareB = n

µµB + n

µhB = 5.07

+1.44−1.12(stat)

nrareB = 1.45

+0.276−0.276(total)

nB = nnon−rareB + n

rareB = 6.53

+2.43−2.43(total)

B(B0s → µ

+µ−

) ≤ 1.6× 10−8

. Substantial improvement with respect to 2006− no pile-up,

√s = 14TeV

+ high-luminosity trigger, no tracker muons, cut-n-count analysisUrs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 21

b-tagging of a different kind

PV

SVIP d

l

track

θ

b Jet Efficiency0 0.2 0.4 0.6 0.8 1

Non

-b J

et E

ffici

ency

-510

-410

-310

-210

-110

CMS Preliminary

Track Counting High PurTrack Counting High EffJet ProbabilityJet B ProbabilitySimple Secondary VtxCombined Secondary VtxSoft Muon By IPSoft Muon By PtRel

Signed 3D IP Significance-40 -20 0 20 40 60 80

Num

ber o

f Tra

cks

in J

et

1

10

210

310

410

510 DATAMC (light jet)MC (charm jet)MC (bottom jet)

= 900 GeVsCMS Preliminary,

Signed 3D IP Significance-40 -20 0 20 40 60 80

Num

ber o

f Tra

cks

in J

et

1

10

210

310

410

510

Number of Tracks at SV1 2 3 4 5 6

Num

ber o

f Sec

onda

ry V

ertic

es

1

10

210DATAMC (light jet)MC (charm jet)MC (bottom jet)

= 900 GeVsCMS Preliminary,

Number of Tracks at SV1 2 3 4 5 6

Num

ber o

f Sec

onda

ry V

ertic

es

1

10

210

CMS-PAS-TRK-10-001

• Not B-flavor tagging, but determination of b vs. udsg jet-origin. impact parameter (wrt primary vertex). secondary vertex reconstruction. leptons


Top Flavor Physics: RCMS-PAS-TOP-09-001

• Top decays to b vs all quarks

R =Γ(t→ bW )Γ(t→ qW )

=|Vtb|2

|Vtd|2 + |Vts|2 + |Vtb|2(in SM)

. |Vtb| measurement (in SM with 3 generations)

. constraints on |Vtb| (in BSM)

• Pi: Probability to find i b-tagged jets

Ai(R; εb, εq) = R2Pi(tt→WWbb)

+2R(1−R)Pi(tt→WWbq)

+(1−R)2Pi(tt→WWqq)

• In 250 pb−1 with dilepton eµ+ 2 jets sampleδR = 0.02stat ⊕ 0.09εb ⊕ 0.03syst

δεb = 0.02stat ⊕ 0.04syst


LHC as a Top Factory

W−

W+t t

b

l

q

q’_

_

b_

+

ν

(µ+ jets: 15%)

CMS-PAS-TOP-08-002

• The LHC at√s = 14TeV is a top ‘factory’

σtot(pp→ tt) ≈ 830pb

. 100-fold increase of cross section wrt Tevatron(LHC at 10/7TeV ≈ 50/20× Tevatron)

. 100-fold increase of (design) luminosity

• Decays. 2/3: t→ qq′

. 11%: t→ `+ν, ` = e, µ

• Example analysis at√s = 14TeV

. isolated muon p⊥ > 30GeV

. jets with ET > 65, 40, 40, 40GeV

. observable: hadronic top 3-jet mass

→ In 10 pb−1

128 signal events90 background events

⇒ or: ‘recoil’ physics . . .Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 24

Top Flavor Physics: Rare Decays

Branching fraction measurements at 5σ

with σsyst

+

without σsyst+

CERN/LHCC 2006-021

• FCNC top decays are an excellent area for BSM searches

• Event selection. 1 isolated high-p⊥ lepton (p⊥ > 20GeV) + 1 high-ET photon (ET > 50GeV). exactly 1 b jet (ET > 40GeV) + 1 non-b jet (ET > 50GeV). 150 < mγq < 200GeV, cos(tγq, tSM) < −0.95→ efficiency ε ≈ 2%


Conclusions and Outlook• CMS has started successfully with data taking at 7TeV

. multitude of light and heavy particles reconstructed as expected

. muon triggers running wide open (compared to ‘high-lumi’ trigger scenarios)

• Heavy flavor physics expectations. for this summer: production (QCD)

quarkonia (cc and bb)inclusive b production cross sectionexclusive b production cross section

bb correlationstt production cross section

. for next year: flavor physics in B (and top) sectorB0s → µ+µ−

B0s → J/ψφ

• Ultimately:. measurement of very rare (leptonic) B0

s and B0d decays

. top flavor ‘recoil’ physics


Flavor physics with CMS: Status and Perspectives · 2 KK mass (GeV/c 1 1.02 1.04 1.06 1.08 1.1 1.12...

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Transcript of Flavor physics with CMS: Status and Perspectives · 2 KK mass (GeV/c 1 1.02 1.04 1.06 1.08 1.1 1.12...