why b physics at pp collider
DESCRIPTION
B physics at the Tevatron S. Donati University and INFN Pisa April 2003 Meeting of the American Physical Society. Why B physics at pp collider. Open wide spectrum of B hadrons B , B 0 , B s , B c , b , b bb cross section is 50-100 m b - PowerPoint PPT PresentationTRANSCRIPT
B physics at the Tevatron
S. Donati University and INFN Pisa
April 2003 Meeting of the American Physical Society
Why B physics at pp collider
CDFCLEO
Open wide spectrum of B hadrons B, B0, Bs, Bc, b, b
bb cross section is 50-100 b ~O(105) larger than @(4S)/Z0
BUT: B hadrons are hidden in a 103
largerbackground (inelastic(pp) 50 mb)
Events more complicated than at (4S)
Crucial detector components:- Tracking system Excellent pt resolution/Vertexing- Trigger Large bandwidth Strong background reduction- Particle identification
CLEO
Tevatron pp colliderMain Injector (new injection stage for
Tevatron)
Ability to accelerate and deliver higher intensity of protons
More efficient anti-proton production
Collision rate: 396 ns crossing time
(36x36 bunches) ~ 2M collisions/sec
Center of Mass energy: 1.96 TeV
Today: luminosity ~4.0 x 1031 cm-2s-1
4 to 7 pb-1/week delivered
Goal: luminosity: ~1032 cm-2s-1
16 pb-1/week delivered
In this talk: results with 70 pb-1 for CDF and 40 pb-1 for D0
CDF Integrated Luminosity
Mar 02
Jan 03
130 pb-1 (delivered)
100 pb-1 (to tape)
B/Charm: ~ 70 pb-1
commiss
CDF Detector in Run II
Tracking System - 3D Silicon Tracker (up to ||~2)
- Faster Drift ChamberTime-of-Flight (particle ID) Plug and Forward Calorimeters DAQ & Trigger system (Online Silicon Vertex Tracker: trigger on displaced vertices, first time at hadron collider)
Completely New:
Inherited from Run I:Central Calorimeter (||<1) Solenoid (1.4T)
Muon system (extended to ||
~1.5)
Partially New:
D0 detector in Run II
B Triggers and data samplesDisplaced trk + lepton (e, )IP(trk) > 120m
Pt(lepton) > 4 GeV
Semileptonic modes
2-Track Trig.Pt(trk) > 2 GeV
IP(trk) > 100 m
Fully hadronic modes
Di-Muon (J/)Pt() > 1.5 GeV (CDF)
J/ modes down to low Pt(J/) (~ 0 GeV)
- CP violation
- Masses, lifetimes
- Quarkonia, rare decays
- High statistics lifetime
- Sample for tagging
studies, mixing
- BS mixing
- CP asymmetry in 2-body charmless decays
(New in CDF/Short term upgrade in D0)
(Conventional)
Primary Vertex
Secondary Vertex
d = impact parameter
BDecay Length
Lxy
Lxy 450m
PT(B) 5 GeV
Sanity check with
known signals:
D0 and
Detector calibration:p scale & B-field
correction
Raw tracks
Add B scale correction
Tune missing material
Correct for material in GEANT
1S
2S
3S
MASS SCALE: MCDF = MPDG-M(Pt)
Use J/ to correct for B field and energy loss:
(scale)/scale ~ 0.02%
D0
Mass measurementsCDF mass (only~20
pb-1)
B+ 5280.6 1.7 1.1 0.8
Bd5279.81 1.9 1.4 0.2
Bs5360.3 3.8 -2.1
(2S) 3686.43 0.54 0.9
CDF
PDGσ
Δ
Ds± - D± mass
differenceBoth D (KK)
m = 99.28 ± 0.43 ± 0.27MeV
PDG: 99.2 ± 0.5 MeV (CLEO2, E691)
Systematics dominated by background modeling
M(Bs) is already the second best in the world (after CDF RunI)
FIRST CDFII
PAPER
2.12.9
See A. Korn’s talk
Background is subtracted
Conventional way to B: J/
L ~ 40 pb-1
75k J/
CDF triggers on stopped J/ : pt() 1.5 GeV/c, pt(J/) 0
CDF can measure cross section down to pT = 0 (first
at hadron collider)
(ppJ/; pT>0; ||<0.6) =
240 1 (stat) 35/28(syst) nb
See Y. Gotra’s Talk
First step: Inclusive B J/X Lifetime
Estimate Estimate B B through through
)(
TT
xyBPFP
ML
MCMC
CDF July 2002 (18 pb-1): =1.5260.0340.035 ps
D0 March 2003 (40 pb-1): =1.5610.0240.074 ps
PDG 2002: = 1.674 0.018
D0 Run II Preliminary
B
D0 Run II Preliminary
J/
B LifetimesHeavy Quark Expansionpredicts the lifetimes
for
different B hadron species
(Bc) << (b0) ~ (b)
< (B0) ~ (Bs) < (B-)
< (b-) < (b)
– (B+)/(B0) = 1.03-1.07
– (Bs)/(B0) = 1.00 + 0.01
– (b)/(B0) = 0.9-1.0
B+/B0 and Bs/B0 measurements agree with prediction
Small discrepancy for b
lifetimes
– LEP + CDF Run I
Exclusive B J/KLifetime (1)
Use exclusively reconstructed B B+ J/ K+
B0 J/ K0* (K0* K)
Bs J/ ( KK)
bJ/ (p)
Simultaneous fitting of
MB: Extract signal fraction
ct: Extract the lifetime
CDF March 2003 (70 pb-1): (B+ )=1.570.070.02 ps
D0 March 2003 (40 pb-1): (B+ )=1.76 0.24 ps
Exclusive B J/K lifetime (2)
(Bs Unique to Tevatron)
CDF Preliminary
B+ 1.57 0.07 0.02
(ps)
Bd1.42 0.09 0.02
(ps)
Bs1.26 0.2 0.02
(ps)
Systemat. & statist. errors already @ Run I level
Use control channels: Bu J/ K+
and Bd J/ K0*
Measurement limited only by statistics
Important for simultaneous measurement
)τ(B)τ(B
d
s
)τ(B)τ(B
d
s
)τ(B)τ(B
d
= 0.89 0.15
= 1.11 0.09 c, [cm]See K. Anikeev’s Talk
CDF: largest fully reconstructedsample in the world: 74 11 evts Yield/Lumi = 2 x RunI
CP asymmetry measures the weak phase of Vts (angle s = 2s )Expected to be very small: sin(2s ) O() 0.03Complicated analysis: requires xs and angular analysis to disentangle CP even/odd final statesCDF reach : sin(2 s )0.1 with 2fb–1 (0.03-0.06 with 10fb–1)
If asymmetry observed with 2fb–1 signal for NEW Physics
We also want to measure the lifetime difference: s = BsH- Bs
L
Current limit (LEP): s / s <0.31 (S.M.: = 0.05 - 0.20)
Physics with B0s J/
More about BJ/ signals
0bJ/ Br.Ratio and Lifetime meas. in
progress (see T. Yamashita, R. Madrak’s Talk)
CDF
D0
B0J/K0s
CDF~220 events
0bJ/
First steps towards sin(2)
Measurement
B+/B0 from lepton+displaced track
CDF: high statistics semileptonic B samplesExcellent calibration samples for B+/B0 lifetime,tagging and B0 mixing BlD0X (D0K): ~10,000 eventsBlD*+X (D*+D0): ~1,500 eventsBlD+X (D+K): ~5,000 events
Run II yieldssignificantly larger,
lower lepton pt threshold possible
thanks to i.ptrigger
CDF CDF CDF
Yield/Lumi ~ Run I x 3 S/N ~ Run I x 2
BS from lepton + displaced track
HIGH STATISTICS SAMPLE:
• Inclusive lifetime:
• Mixing (moderate xs):
good S/N, limited time resolution: back-up sample
Bs Dsl [] l [[KK] ]l ONLY @ Tevatron
Efficiency vs c
MC
AR
BIT
RA
RY
UN
ITS
Systematics of trigger bias
)τ(B)τ(B
d
s
385 22 Ds
(muon only)
b from lepton+displaced track
• Branching Ratio
• Measure
Q2 = m(l)
important for theory
Experimental challenge:
disentangle from decays through excited baryons
b cl [pK] l
Yield/Lumi = 4 x RunI
S/N ~ 2 x Run I
2dQdΓ
Γ1
Time of flight
dE/dx +
Physics with the hadronic trigger
Reconstructed large (0.5M) D mesons:D K, D0 K, D* D0, Ds D0 KK, D0 See K. Stenson’s (Charm Physics review), C. Chen (D x-section), S. Vallecorsa (D Cabibbo supp. decays), M. Campanelli (D orb. excited states) talks for CDF Charm results
D’s from Primary Vertex have d 0
Direct Charm
D0K 86.5 0.4 %
(stat)
D*D0 87.6 1.1 % (stat)
DK 89.1 0.4 %
(stat)
Ds 72.4 3.4 % (stat)
B fraction 10 - 20
%
D mesons I.P. (d) distribution
D
d(D)
D
B
CDF: open access to fully hadronic D and B signals
Ingredients for B0s mixing
Nunmix(t) – Nmix(t)
Nunmix(t) + Nmix(t)= Dcos(mst)Amix(t) =
1. Reconstruct the final state (use fully rec. B0s → D-
s
π+(3π))with good S/B (thanks to precise tracking, vertexing, PID)
60 fs (SVX II detector)45 fs (also Layer 00 is used)
3. Identify the flavor of Bs at production: B-flavor tagging algorithms
2. Measure proper decay time: ; = PT(B) / M(B) c = Lxy
Error on B momentum, ~ 15% (semileptonic)negligible (~ 0.5%) forfully reconstructed final states
Current limit:
ms 14.4 ps-1
ms/md
First steps towards B0s mixing in
CDF Bs Ds
(*) [] [[KK] ]
Fully reconstructed
Bs is consistent with
Bd D control sample
Collect more data and understand tagging
See S. DaRonco’s Talk
B Flavor Tagging
OST (opposite side tagging): B’s produced in pairs measure flavor of opposite B
“Identify the flavor of B at production”
JETQ: sign of the weighted average charge of opposite B-JetSLT: identify the soft lepton from semileptonic decay of opposite BSST (same side tagging):
B0 (B0) is likely to be accompanied close by a + ()
Search for the track with minimum PTREL
Figure of merit:
= efficiency ;
Effective size of sample is reduced by D2
D = “Dilution” = 1 – 2Pmistag
D2 “tagging effectiveness” 2%
bd
du
u
B0
+
NEW in CDF: “Kaon b-taggers”• Exploit K/ separation of new TOF
• Well suited for strange B mesons
Same Side K: a B0s (B0
s) is likely to be accompanied close by a K+ (K) from fragmentation
bs
su
u
B0s
K+
Jet charge tag Muon tag
63.0 3.6 %
= 8.3 1.9%
D=15.8 8.3 % D=44.4 21.1 %
2.4 1.7% 3.3 1.8 %
D0 Run II Preliminary
For CDF studies see A. Ratikin and T. Moulik’s Talks
Opposite Side K: due to bcs it is more likely that a B meson contains in final state a K than a K+ to identify a B0
s look for a K from the decay of the opposite B
Strategy for disentangling channels:- Invariant mass shape (M ~25 MeV)- Kinematical variables- Particle Identification - Oscillation of CP asymmetry
300 events in 65 pb-1 of CDF Hadronic Trigger data with very good S/B
B0 h+h- is a mixture of
Bd; BdKBsKBsKK
Physics with B0 h+h-
Can soon perform interesting measurements:• Relative B. Ratios: Bd /; Bs KK/K• Direct CP asymmetries in Bd Kself tagging)• CP asymmetries in Bd (with b-tagging)
Later on: CKM angle
CDF II simulation
—sumBdKBsKK
Bd
BsK
( inv.mass)
Use K/ separation dE/dx
1.16
Disentangling the B0h+h-
contributionsUse M vs (1-p1/p2)q1
See M. Morello’s talk
B0d B0
d K- B0d K+
B0s K+ B0
s K-B0s KK
Expected fraction res. (MC 65 pb-1)B0
d K(0.6): 0.062 (stat)
B0 d(0.15): 0.056 (stat)
B0sKK(0.2): 0.045 (stat)
B0 sK(0.05): 0.036 (stat)
ACP(B0d
K): 0.14 (PDG-2002: 0.06)
Angle from B0h+h-
B0 + has two (comparable) decay amplitudes:
Tree Penguin
b
d
W+u
d
u
+
B0 d
ACP(t) = ACP dir cos(md t) + ACP
mix sin(md t)
ACPdir, ACP
mix functions of , , d, (d ei P / T decay amplitude)
direct CP CP from mixing alone
R. Fleischer (PLB 459 (1999) 306): Assume U-spin symmetry (d s)Similar relation holds for Bs K+K (md replaced by ms)The 4 asymmetries can be expressed as function of , and P/T amplitude ratio
Parameters can be extracted from fit of meas. of ACP(t) for Bd and BsKK
d
b W+
u
+
B0 u,c,t
d
d
u
(SU(3) breaking effects)Expected (2fb-1) accuracy: () = ±10(stat) ±3(syst)
g
ms/md
Hadronic b c signal
• Measure mass, lifetime, polarization
• Precise Lifetime
Discrepancy with theory:Is it valid for baryons ?
b c [pK]
Largest fully rec. hadronic channel
)τ(B)τ(Λ
0b
NO PID YET
pK Mass [GeV]
pK Mass [GeV]
See Y. Li’s Talk
Conclusions The upgraded CDF/D0 detectors are taking new data Great B physics potential, we have results on:
- Masses, lifetimes in the BJ/K exclusive channels and production cross sections- New impact parameter trigger (CDF-only): huge/clean semileptonic/all hadronic B signals (and also Charm):
- Large and clean BlDX reconstructed in CDF (excellent for lifetime, tagging and md
meas.)
- B0s → D-
s π+: first ingredient towards ms
- B0h+h-: important results awaiting on our
way to (B0
sKK, CP in B0dK)
Lots of Beauty (and Charm) at the Tevatron
Backup Slides
CDF Integrated Luminosity
Mar 02
commissioning
Data used for Today’s results Mar 02 – Jan 03
130 pb-1 (delivered)
100 pb-1 (to tape)
B/Charm: ~ 70 pb-1
Jan 03
B physics prospects(with 2fb-1)
Bs mixing: Bs →Dsπ(Ds3π) (xs up to 60, with xd meas. one side of U.T.)
Angle : B0→ J/ψ Ks (refine Run1 meas. up to (sen2) 0.05)
CP violation, angle γ : B0→ ππ(πK), Bs → KK(Kπ)
Angle s and s/ s : Bs→ J/ψ (probe for New Physics)
Precise Lifetimes, Masses, BR for all B-hadrons: Bs, Bc, Λb … (CDF observed: Bc → J/ψ e(). Now hadronic channels Bc → Bs X can be explored)
HF cross sections (beauty and charm)
Stringent tests of SM … or evidence for new physics !!
Both competitive and complementary to B -factories
Sin(2) in B0J/Ks
N(B0)(t) - N(B0)(t)
N(B0)(t) + N(B0)(t)=Dsin(2)sinmd
tACP(t) =
N(J/ Ks) from scaling Run I data:• x 20 luminosity
8,000• x 1.25 tracks at L1 trigger 10,000• x 2 muon acceptance 20,000• Trigger on J/ e+e + 10,000
In Run1 measured:
sin(2)=0.79±0.39±0.16
B0 J/ Ks ; J/
(400 events)(+60 B0 (2S) Ks)
sin(2)=0.91±0.32±0.18
Combined D2: from 6.3% to 9.1% (Kaon b-tag)
Same S/B = 1
Expect: s(sin2b) 0.05
With 2fb-1 can refine this measurementAlthough: no way to compete with B-Factories !
)) (2 sin( S B
ND1
2
1Stat. Error:
Systematic ~ 0.5xStatistical
(scales with control sample statistics)
ms/md
Tevatron Performance
July ‘01
Now
Tevatron operations • Startup slow, but progress steady !
• Now: L ~3.5 x 1031 cm-2s-1
integrating ~ 6. pb-1/week• … still factor 2-3 below planned valuesadditional improvements (~10-20%) expected from Jan. 3weeks shutdownCDF operations
• Commissioning: Summer 2001• Physics data since February 2002• Running with >90% Silicon integrated
since July 2002
Initial Luminosity3.8 x 1031
110 pb -1
July ‘02
On-tape Luminosity
Luminosity (on-tape): ~20pb-1 until June (analyses in this talk) Additional 90pb-1 July – December Reach 300- 400 pb-1 by October 2003
Feb ‘02
Quadrant of CDF II Tracker
LAYER 00: 1 layer of radiation-hard silicon at very small radius (1.5 cm) (achievable: 45 fs proper time resolution in Bs Ds )
COT: large radius (1.4 m) Drift C.
• 96 layers, 100ns drift time • Precise PT above 400 MeV/c
• Precise 3D tracking in ||<1
(1/PT) ~ 0.1%GeV –1; (hit)~150m
• dE/dx info provides 1 sigma K/ separation above 2 GeV
SVX-II + ISL: 6 (7) layers of double-side silicon (3cm < R < 30cm)• Standalone 3D tracking up to ||= 2• Very good I.P. resolution: ~30m (~20 m with Layer00)
TOF: 100ps resolution, 2 sigma K/ separation for tracks below 1.6 GeV/c (significant improvement of Bs flavor tag effectiveness)
TIME OF FLIGHT
CDF II Trigger System3 levels : 5 MHz (pp rate) 50 Hz (disk/tape storage rate) almost no dead time (< 10%)
XFT: “EXtremely Fast Tracker” 2D COT track reconstruction at Level 1
• PT res. pT/p2T = 2% (GeV-1)
• azimuthal angle res. = 8 mrad
SVT: “Silicon Vertex Tracker” precise 2D Silicon+XFT tracking at Level 2
• impact parameter res. d = 35 m
Offline accuracy !!
CAL COT MUON SVX CES
XFT XCES
XTRP
SVTL2
CAL
L1CAL
GLOBALL1
L1MUON
L1TRACK
GLOBALLEVEL 2 TSI/CLK
CDF II can trigger on secondary vertices !! Select large B,D samples !!
Matched to L1 ele. and muonsenhanced J/ samples
SVT: Triggering on impact parameters
d
beam spot
COT track ( 2 parameters) 5 SVX coordinates
Impact Parameter (transverse projection)
• Combines COT tracks (from XFT) with Silicon Hits (via patternmatching) • Fits track parameters in the transverse plane (d, , PT) with offline res.• All this in ~15s !• Allows triggering on displaced impact parameters/vertices• CDF becomes a beauty/charm factory
~150 VME boards
B triggers: conventional
Suffer of low BR and not fully rec. final state
Need specialized triggers(bb) / (pp) 10-3
CDF Run1, lepton-based triggers:
Di-leptons (, PT 2 GeV/c): B J/ X, J/ Single high PT lepton ( 8 GeV/c): B l D X
Now enhanced, thanks to XFT (precise tracking at L1) :• Reduced (21.5 GeV/c) and more effective PT thresholds • Increased muon and electron coverage• Also J/ ee
Nevertheless, many important measurements by CDF 1: B0
d mixing, sin(2), B lifetimes, Bc observation, …
XFT performance
XFT: L1 trigger on tracks better than design resolution
pT/p2T = 1.65% (GeV-1)
= 5.1 mrad
XFT track
Offlinetrack
Efficiency curve: XFT threshold at PT=1.5 GeV/c
= 96.1 ± 0.1 % (L1 trigger)
53.000 J/
11 pb-
1
SVT performance
D0 K used as online monitor of the hadronic SVT triggers
I.P. resolution as planned
d = 48 m = 35 m 33 m
Efficiency
80%
90%
soon
transverse beam size
intrinsic
S/B 1
TOF performance TOF resolution (110ps)
within 10% of design value
with TOF PID
S/N = 1/40
S/N = 1/2.5
Background reduction in KK:Low PT (< 1.5 GeV/c) track pairsbefore and after a cut on TOF kaon probabilityx20 bkg reduction, 80% signal efficiency
CDF J/cross section
0<pt<0.25
GeV 5.0<pt<5.5 GeV10.0<pt<12.0 GeV
(ppJ/; pT>0; ||<0.6) =240 1 (stat) 35/28(syst) nb
Lots of charm from hadronic triggers:
Foresee a quite interesting charm physics program:• D cross sections, • CP asymmetries and Mixing in D sector, Rare decays, …
56320490
K mass
D0 K
KK mass mass
D0 KK D0
5670180 2020110
(DKK)/(DK) = 11.17 0.48(stat) 0.98 (syst) %(D )/(DK) = 3.37 0.20(stat) 0.16(syst) %
Relative Br. Fractions of Cabibbo suppressed D0 decays :
Already competitivewith CLEO2 results(10fb-1 @ (4S))
!!!!!
With ~10 pbWith ~10 pb-1-1 of “hadronic trigger” data: of “hadronic trigger” data:
O(107) fully reconstructed decays in 2fb-1
B0s mixing: expectations with
2fb-1
Signal: 20K ( only) - 75K (all) events• with SVT hadronic trigger
• BR (Ds ) = 0.3 % ; BR (Ds ) = 0.8 %
Resolution: (c) = 45 fs (with Layer00)
D2 = 11.3% (with TOF)
S/B: 0.5-2 (based on CDF I data)
5 sensitivity up to:
Xs = 63 (S/B = 2/1)
Xs = 53 (S/B = 1/2)
S.M. allowed range: 20. < Xs < 35.
Can do a precise measurement… or evidence for new physics !
xs = ms(B0s)Bs Ds, Ds
Ds , K*K,
2( m )22
1 1 S B( x )
N D Ss t
s e
Projections for xs reach with 2fb-1
Xs = 42-63
Optimistic: S/B =2/1 Conservative: S/B =1/2
MC simulation: accounts also for SVT cuts on proper time acceptance,non-Gaussian tails in proper time resolution function
Xs = 32-53