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...
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...
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 3
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 4
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 5
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 6
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 7
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 9
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 10
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 11
Candidate decay Ξ+→ Λ(→ pπ+)π+
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 12
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 13
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 14
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 15
. . . 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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 16
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 19
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 20
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 22
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 23
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%
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 25
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
Urs Langenegger Flavor physics with CMS: Status and Perspectives (2010/05/25) 26