lhcb status and charm physics program - cornell universitylhcb status detector construction nearing...
TRANSCRIPT
-
xford
hysics
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
-
xford
hysics
Outline
LHCb status
LHCb’s trigger
CP violation searches in D decays at LHCb
Charm mixing measurements at LHCb
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 2/18
-
xford
hysics
Large Hadron Collider
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 3/18
-
xford
hysics
LHCb detector
250mrad
100mrad
M1
M3M2
M4 M5
RICH2HCAL
ECALSPD/PS
Magnet
T1T2T3
z5m
y
5m
− 5m
10m 15m 20m
TTVertexLocator
RICH1
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 4/18
-
xford
hysics
LHCb status
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 5/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 5/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 6/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 7/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 8/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 9/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 10/18
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 11/18
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
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 12/18
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
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 13/18
-
xford
hysics
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
-
xford
hysics
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)
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 15/18
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
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 16/18
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
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 17/18
http://indico.cern.ch/materialDisplay.py?contribId=18&sessionId=0&materialId=slides&confId=12011http://mlm.home.cern.ch/mlm/FlavLHC.html
-
xford
hysics
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
Charm 2007: International Workshop on Charm Physics — 08 August 2007 – p. 18/18
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