LHCb status and charm physics program - Cornell UniversityLHCb status Detector construction nearing completion Detector commissioning is in progress The full LHCb detector will be

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LHCb status and charm physicsprogram

Patrick Spradlin

University of Oxford Particle Physics

On behalf of the LHCb collaboration

Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 1/18

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Outline

LHCb status

LHCb’s trigger

CP violation searches in D decays at LHCb

Charm mixing measurements at LHCb


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Large Hadron Collider


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LHCb detector

250mrad

100mrad

M1

M3M2

M4 M5

RICH2HCAL

ECALSPD/PS

Magnet

T1T2T3

z5m

y

5m

− 5m

10m 15m 20m

TTVertexLocator

RICH1


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LHCb status


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LHCb status

Detector construction nearing completion

Detector commissioning is in progress

The full LHCb detector will be ready tocollect data by the projected LHC startup in May 2008


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LHCb features

The features that make LHCbexcellent for B physics also make it agood charm physics experiment

High event rate

Excellent vertexing and proper timeresolution: ∼ 45 fs for secondary D0

Good tracking and momentumresolution: ∼ 6 MeV D0 mass

Excellent K-π discrimination


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LHCb trigger

L0 hardware trigger — high pt particlesIncluding Calorimeter hadrons Et >∼ 3.6GeV; Muon pt >∼ 1.5GeVInput 40 MHz → 1 MHz outputEfficiently favors bb events over prompt charm

HLT software triggerParallel trigger paths: ‘alleys’

Partial reconstruction of limited detector informationQuickly identify general B event features- High pt particles (hadrons, muons, electrons, and photons)- Charged tracks with sizable impact parameter

Followed by channels for specific interesting decaysFast final state candidate reconstructionComposite decay chain reconstruction, e.g., D∗+ → π+s D0(h−h+)

2 kHz total output rate300 Hz D∗+ → π+s D0(h−h+)600 Hz Di-muon events

200 Hz Exclusive physics channels900 Hz Single muon inclusive


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Uses of LHCb D∗+ trigger

RICH calibration

(MeV)πK - mπ Ksπm = m∆140 145 150 155 160

frac

tio

n /

0.5

MeV

bin

0

0.05

0.1

0.15

0.2

0.25

0.3RS signal

WS double mis-ID background

backgroundsπWS random

WS combinatoric background

effEntries 20

Mean 51.03

RMS 27.47

Kaon P(GeV)10 20 30 40 50 60 70 80 90 100

rati

o0

0.2

0.4

0.6

0.8

1

effEntries 20

Mean 51.03

RMS 27.47

purityEntries 20

Mean 67.94

RMS 27.02

purityEntries 20

Mean 67.94

RMS 27.02

effEntries 20

Mean 50.66

RMS 27.62

effEntries 20

Mean 50.66

RMS 27.62

purityEntries 20

Mean 67.68

RMS 27.33

purityEntries 20

Mean 67.68

RMS 27.33

MC truth L0, L1, HLT trig. ev

Using L0, L1,HLT loose cut calibr. sample

eff

K → K, p

π → K, p

Charm physics


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Two sources of charm

B decays (B → D(∗)X)+ Strongly favored by LHCb triggers

+ Potentially less background

- New techniques need to be developed—no published measurements

Prompt production in primary interaction0 Triggered less efficiently—compensated by prolific production

- Potentially larger backgrounds—especially random πs background for D∗+

+ CDF has proven that measurements are possible in hadronic environment

Estimated reconstructible yieldsin 2 fb−1 from B → D∗+X

(Similar yields expected from prompt production)

D0 → K−π+ 50 × 106

D0 → K−K+ 5 × 106

D0 → π−π+ 2 × 106

D0 → π−K+ 0.2 × 106


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CP violation searches

Looking for unambiguous signs of New Physics inas many channels as possible(A vital part of any charm physics program)

Both time integrated and time dependent CPV searches

Two body Kπ, K−K+, and π−π+ modes

Three body charged and neutral decaysAmplitude analyses

D0 → KSπ+π−, KSK+K−, KSKπ; D+ → K+K−π+, Kππ

Four body decaysQuantities odd under T

Amplitude analyses (analysis code already exists in LHCb)

D0 → K+K−π+π−, Kπππ


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CPV in D0 → K−K+

Data set N(K−K+) ACP(K−K+)(%) ACP(π−π+)(%)

CDF 123 pb−1 16220 2.0 ± 1.2 ± 0.6 1.0 ± 1.3 ± 0.6Bellea 540 fb−1 109000 0.15 ± 0.35 ± 0.15 −0.28 ± 0.52 ± 0.15BaBara 91 fb−1 26084 −1.3 ± 0.8 ± 0.2 0.3 ± 1.1 ± 0.2LHCb 10 fb−1 8 × 106 Lower limit yield from D∗+ from B, not

optimized for time-independent K−K+

a Asymmetries of τ(K−K+) rather than Γ(K−K+)

CDF direct CPV search in K−K+

]2

KK Mass [GeV/c1.75 1.8 1.85 1.9 1.95

2E

ntr

ies/

3 M

eV/c

0

1000

2000

3000

4000

5000

+π]+K-[K→+π0D→*+D+ charge conjugate

CDF II

]2 Mass [GeV/cππ1.78 1.8 1.82 1.84 1.86 1.88 1.9

2E

ntr

ies/

4 M

eV/c

0

1000

2000

3000

4000

5000

+π]+π-π[→+π0 D→*+D+ charge conjugate

CDF II


http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0504006http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0703036http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0306003http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0504006

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Mixing measurements at LHCb

Precise mixing measurementsMeasure CP violation in mixingDetermine relative values of x and y—dominant mixing processes

WS D0 → π−K+ mixing analysisSensitive to x′2 and y′

BaBar 3.9σ evidence Phys.Rev.Lett.98:211802,2007 (hep-ex/0703020)Require measurement of strong phase δ by CLEO / BES-III to relate x′, y′ to x, y

Two body lifetime ratio measurement of yCPSCS D0 → K−K+ and π−π+

Belle 3.2 σ evidence Phys.Rev.Lett.98:211803,2007 (hep-ex/0703036)

Amplitude analysis of D0 → KSπ+π−

Sensitive to x and y Powerful technique demonstrated by CLEO and Belle

Mixing measurements in D0 → 4hTechnology for 4-body amplitude analysis already exists at LHCbPreliminary selection: up to 25 × 106 RS D0(4h) events per 2 fb−1 written to tape


http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0703020http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0703036http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0503045http://www.slac.stanford.edu/spires/find/hep/www?eprint=arXiv:0704.1000

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D∗ vertex resolution

D∗ resolution in z

m)µ (MC - zrecz-40000 -20000 0 20000 40000

m b

inµ

can

d /

800

0

200

400

600

800

1000

1200

Decay vertex resolutions

D0 D∗+

x 21.6 µm 187. µm

y 16.9 µm 144. µm

z 257. µm 4232. µm

τ 0.465 ps

Signal MC lab frame angles

1,2θcos0.98 0.985 0.99 0.995 1

bin

-4 1

0×

can

d /

2

0

200

400

600

800

1000

1200

daughter angle0Lab Frame D

angle+sπ-0Lab Frame D

D0 and π+s almost collinear

Add tracks at birth vertex

D0 lifetime τ :(0.4101 ± 0.0015) ps

D0 flight distance at 60 GeV:βγcτ ≈ 4 mm


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Birth vertex improvement

Use additional tracks at production vertex

76% of D∗+ from B’s have at least onecharged sister

63% have reconstructed sister tracks thatpass some basic criteria

Use one additional track partiallyreconstruct parent Bpart

Decay vertex resolutions

D0 D∗+ Bpart

x 21.6 µm 187. µm 18.1 µm

y 16.9 µm 144. µm 18.4 µm

z 257. µm 4232. µm 237. µm

Improved proper time resolution = 0.045 ps

1.07 < B/S = 2.56 < 5.28 at 90% CL

/ ndf 2χ 34.65 / 45Normalization 0.37± 12.83 Core fraction 0.0778± 0.5255 Mean 0.002034± -0.001338 Core sigma 0.00397± 0.04498 Second sigma 0.0101± 0.1114

(ps),gen0D

τ - ,rec0D

τ-0.2 -0.1 0 0.1 0.2

can

d /

0.01

ps

bin

0

10

20

30

40

50

60

70

80

90 / ndf 2χ 34.65 / 45

Normalization 0.37± 12.83 Core fraction 0.0778± 0.5255 Mean 0.002034± -0.001338 Core sigma 0.00397± 0.04498 Second sigma 0.0101± 0.1114

lifetime (ps)0D-1 0 1 2

can

d /

0.06

ps

bin

0

20

40

60

80

100

120

140

160 lifetime, reconstructed0D

lifetime, generated0D

Process detailed in CERN-LHCb-2007-049Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 14/18

http://cdsweb.cern.ch/record/1045412

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Toy MC study of WS mixing

Investigate sensitivity to x′2 and y′ 1-D fit to proper time

Γ(t; D0 → π−K+) ∝ e−Γtˆ

RD +√

RDy′Γt + 1

4(y′2 + x′2)(Γt)2

˜

10 fb−1 of simulated signal ev/toy

Exponential background exp (−t/τD0 )

Acceptance and resolution effects includes

Fit to x′2 and y′Proper Time (ps)

0 1 2

Lo

g E

ven

ts /

0.03

ps

bin

1

10

210

310

410

510

Proper Time (ps)0 1 2

Lo

g E

ven

ts /

0.03

ps

bin

1

10

210

310

410

510DataSignal + Background

DCS SignalBackground

InterferenceMixing

Data set NWS x′2(×10−3) y′(×10−3)BaBar 384 fb−1 4030 −0.22 ± 0.30 ± 0.21 9.7 ± 4.4 ± 3.1Belle 400 fb−1 4024 < 0.72 −9.9 < y′ < 6.8

HFAG average −0.01+0.20−0.20 5.5

+2.8−3.7

B factories 2 ab−1 x′2 ± 0.15 y′ ± 3.0LHCb 10 fb−1 232500 x′2 ± 0.064 (stat) y′ ± 0.87 (stat)


http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0703020http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0601029http://www.slac.stanford.edu/xorg/hfag/charm/index.html

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Toy MC of lifetime ratio

Compare lifetimes of the non-eigenstate RS decayD0 → K−π+ and CP even decays D0 → K−K+(π−π+)

yCP ≡τ(D0→K−π+)

τ(D0→(K+K−,π+π−) − 1 = y cos φ − x sin φ[

R2m−12

]

2 fb−1 of simulated signal ev/toy

Exponential background exp (−t/τD0

)

Acceptance and resolution effects includes

Data set N(K−K+) yCP(%)

Belle 540 fb−1 109000 1.31 ± 0.32 ± 0.25BaBar 91 fb−1 26084 1.5 ± 0.8 ± 0.5

HFAG average 1.12 ± 0.32B factories 2 ab−1 yCP ± 0.3LHCb 10 fb−1 8 × 106 yCP ± 0.05 (stat)

Acc

epta

nce

/ ndf 2χ 6.48 / 9Asymptote, A 6.47± 67.35

i

Intercept, r 0.1048± 0.6779 accΓ 2.710± 2.481

proper time (ps)0D0 0.5 1 1.5 2

can

d /

bin

0

10

20

30

40

50

60

70

/ ndf 2χ 6.48 / 9Asymptote, A 6.47± 67.35

i

Intercept, r 0.1048± 0.6779 accΓ 2.710± 2.481

Res

olut

ion

/ ndf 2χ 34.65 / 45Normalization 0.37± 12.83 Core fraction 0.0778± 0.5255 Mean 0.002034± -0.001338 Core sigma 0.00397± 0.04498 Second sigma 0.0101± 0.1114

(ps),gen0D

τ - ,rec0D

τ-0.2 -0.1 0 0.1 0.2

can

d /

0.01

ps

bin

0

10

20

30

40

50

60

70

80

90 / ndf 2χ 34.65 / 45

Normalization 0.37± 12.83 Core fraction 0.0778± 0.5255 Mean 0.002034± -0.001338 Core sigma 0.00397± 0.04498 Second sigma 0.0101± 0.1114


http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0703036http://www.slac.stanford.edu/spires/find/hep/www?eprint=hep-ex/0306003http://www.slac.stanford.edu/xorg/hfag/charm/index.html

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Summary of LHCb at 10 fb−1

2x-0.1 -0.05 -0 0.05 0.1 0.15 0.2 0.25 0.3

-310×

y

0.004

0.0045

0.005

0.0055

0.006

0.0065

0.007

0.0075

0.008

0.0085

2x-0.1 -0.05 -0 0.05 0.1 0.15 0.2 0.25 0.3

-310×

y

0.004

0.0045

0.005

0.0055

0.006

0.0065

0.007

0.0075

0.008

0.0085

WS 1-signaWS 2-sigmaWS 3-sigmaYcp 1-sigmaYcp 2-sigmaYcp 3-sigma

Combined Mixing Results

Values for x′2 and y′ from David Asner’s March 2007 report toFlavour in the era of the LHC


http://indico.cern.ch/materialDisplay.py?contribId=18&sessionId=0&materialId=slides&confId=12011http://mlm.home.cern.ch/mlm/FlavLHC.html

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Summary

We have only begunto tap LHCb’s potentialfor charm physics

LHCb will be complete and ready to takedata at LHC start-up in May 2008

The LHCb experiment has an excitingpotential for charm physics studies

A dedicated D∗ trigger will provide 108 flavortagged D0 → hh per 2 fb−1

Unprecedented sensitivity in searches for:D0 mixing

CP violation


Outline Large Hadron Collider LHCb detector LHCb status LHCb status

LHCb features LHCb trigger Uses of LHCb $D^{ast +}$ trigger Two sources of charm CP violation searches CPV in $D^{0} ightarrow K^{-}K^{+}$ Mixing measurements at LHCb $D^{*}$ vertex resolution Birth vertex improvement Toy MC study of WS mixing Toy MC of lifetime ratio Summary of LHCb at $10,mathrm {fb}^{-1}$ Summary

Documents

LHCb status and charm physics program - Cornell UniversityLHCb status Detector construction nearing completion Detector commissioning is in progress The full LHCb detector will be