why b physics at pp collider

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