preparation of b scan jianchun wang syracuse university cleo meeting 04/13/02

Preparation of b Scan

Jianchun Wang

Syracuse University

CLEO Meeting04/13/02

04/13/02 Jianchun (JC) Wang 2

People Involved

Basit Athar, Raja Nandakumar, Jianchun Wang

Sheldon Stone, John Yelton, Steve Blusk

David Kreinick, Jean Duboscq

Others


Motivation of b Study

See February’s talk by JC/Sheldon

b lifetime, mass precision (current: 9 MeV), absolute branching ratio

Necessary for determining Vcb via bcl Provide input to hadron collider b experiments for

Vcb, production rate, etc …

This is possible if the bb cross-section is large enough


Events at b Threshold

We hope to have 50 pb for bb pair production. For the study, we use MC simulated events for this portion.

The contribution from udsc is similar to that of (4S), with decreasing of cross-section due to CM energy. We use off-resonance data here.

Most of bb events produce B mesons. We use on-4S resonance data ( subtracted by off-resonance data ) for this part, with cross-section adjusted to 200pb.


Signature of b Events

It has BB-like event shape ( we require R2<0.2 to reject continuum background).

The c production rate is very large ( ~ 100% per b , compared to 6.4% per B). Hence counting number of reconstructed c is a direct tool.

The proton and lepton production rate is also high, and reconstruction efficiency is big. So requiring both proton and lepton in same event is even better.

We also count number of proton, and hadronic event in the scan.


c Decay Modes

0.0870.0530.6390.270.83 0.0883.31.38

0.1030.0570.6390.270.80.26 0.0363.61.37

0.0900.2000.6390.270.8 0.1400.90.36

0.1450.0850.260.83 0.1303.41.0pK5

0.0660.0510.50.6860.390.83 0.0682.60.7pK4

0.0440.0270.50.6860.80.390.26 0.0283.31.0pK3

0.1380.1200.50.6860.80.39 0.1102.30.6pK2

( 0.02 )0.4000.83 0.5105.01.3pK1

Br

Br(pK)

Measured Eff ()

Estimated

Efficiency

Br (%)Modes

Not all modes will be used in scan, But most of them can be used in further study


Brief Selection Criteria

Good tracks.

P/K/: Dedx, Grand LL (combine Dedx, RICH info).

Electron: Dedx, X925, E/P, Grand LL.

Muon: Dedx, Mudepth.

: X925, Barrel, no track matching, cosCM.

KS: Fit quality(prob>0.01), Distance(r-) > 2mm.

: Fit quality(prob>0.01), Distance(r-) > 1mm.


Decay Mode pK

Scaled to 12 pb.

Sum of three sources: bb pair, BB pair, and udsc continuum.

About 20 c from b can be seen.

MpK (GeV)

Nu

mb

er o

f E

ntr

ies

/ 2 M

eV


Decay Modes PKs and N

um

ber

of

En

trie

s / 2

MeV

MpKs (GeV) M (GeV)

Two modes add 23% more to pK mode


Sum of Three Modes

S/S+N 3

0.31.50.00.10.51.8

BackgroundC signal

33.27.824.2Sum

0.51.40.00.20.72.8pKS

7.519.82.22.34.019.6PK

BudscbBudscb


Proton Lepton Event

Require at least one muon or electron in the event.

With R2 < 0.2 cut.

The efficiency for bb event is 17%.

With 12 pb, reconstruct: 103.3 from bb events.

80.3 from udsc continuum. 30.1 from BB events.

S/S+N = 7.1.XPp

Nu

mb

er o

f E

ntr

ies

/ 0.0

1


Proton Lepton EventN

um

ber

of

En

trie

s / 0

.01


Proposed Scan Plan At 61032, we expect 16 pb /day.

12 pb per point, total 27 points.

36pb (equivalent to 3 points) at 11230 MeV.

With 6 MeV interval, scan 7 points till ~11270 MeV.

Take 1 point at the end of the scan region (11380 MeV).

By then we should have enough information to decide where to go next.

Should we find a resonance or a large cross-section point, we will stop the scan and take as much data as possible at that point.


Computation Resources

We expect to have useful information in 24 hours.

David Kreinick and Jean Duboscq estimated the CPU consumption and allocate enough computers for the scan.

Methods to reduce CPU burden: tighter filter, fast RICH algorithm, …

Save PDS data on disk: ~ 64GB.

Save only “hot-store” information.


Beam Condition

Hello,

A few minutes ago we began collecting our first

collisions at 5.6 GeV. Luminosity at 268 (10**30) - not too

bad for the first fill. Crate 5 on DR went thru major surgery

today during access so we are still evaluating its performance.

I'll let you know how things go.

Dan

Dan Cronin-Hennessy message (03/20/02)


What’s Next?

Possible things to do with b data sample

Combine c with a pion or rho to measure b mass.

Inclusive semileptonic decay bclX

Measure bb production with double reconstrucedc.

Measure bb production with proton lepton ( this requires good MC).

…


Tuning Decay Table

DECAY LAMB

CHANNEL 1 0.1020 NUEB E- LAMC

CHANNEL 1 0.1020 NUMB MU- LAMC

CHANNEL 0 0.0400 LAMC PI-

CHANNEL 0 0.0100 LAMC RHO-

CHANNEL 0 0.0200 LAMC A1-

CHANNEL 0 0.0200 LAMC DS-

CHANNEL 0 0.0400 LAMC DS*-

CHANNEL 0 0.0010 ETAC LAM

CHANNEL 0 0.0050 PSI LAM

CHANNEL 0 0.0200 LAMC PI+ PI- PI-

CHANNEL 0 0.0200 LAM K0 PI+ PI+ PI- PI-

CHANNEL 0 0.0200 P+ D0 PI-

CHANNEL 0 0.4300 LAMC *DU*

CHANNEL 0 0.0800 SIGC+ *DU*

CHANNEL 0 0.0700 CCS1 *DU*

CHANNEL 0 0.0100 P+ *DU*

CHANNEL 0 0.0100 CSU1 *DU*

ENDDECAY

With reference to B decays, Steve adjusted the decay table.

The effect to the two estimations presented here may be small. And we are checking on this.


Acknowledgement

We really want to thank following people for their help on the coding:

Alan Magerkurth

Hanna Mahlke-Krueger

Hajime Muramatsu

And many others we bugged


Summary

The scan tools are tested and ready.

The proton-lepton method is more effective.

CPU estimation and resource reallocation is going on.

We are mostly ready for the scan.


Track Selection Criteria Dedx information valid, and 3 consistence.

Grand LL: LL(K)-LL(pi)+Nsig(K)**2 – Nsig(pi)**2

RICH valid, P(K)>0.5 Gev, P(p)> 1GeV: Grand LL < - 4

Others: (no RICH), Grand LL < -4

Number of expected hits > 0, and number of hits > half of the expected.

Number of expected hits in fit > 0, track fitted, fit not abort.

Fit helix valid, track quality valid, track fit, not abort, degreesOfFreedom > 0, D0 < 0.6cm (0.35), Z0 < 5cm.


Reconstruction of c

cpK

Br ~ 0.05 0.83 ~ 0.025

= 5.4 MeV


Missing mass calculation: (b X

Since P is relatively small, and cos is unknown, conventionally the last term is treat as 0.

In fact the resolution can be improved by giving cos a fixed value, this is due to the boost of b.

Semi-leptonic Mode: bc+

cos22

)(22

)()(

22

22

222sin

XXX

XXX

XXgmis

PPEEMM

PPEEMM

PPEEM


None-zero cos

ECM Mb = 140 MeV

MC at generator level

cos = <cosMC>


None-zero cos

• Effect of boost is stronger with more kinetic energy.

• Reconstruction efficiency depends on the boost mainly due to P>GeV requirement.

• cos is fixed to <cosMC> of reconstructed event.

ECM2Mb (MeV)


The Effect of Beam Energy

ECM2Mb (MeV) ECM2Mb

(MeV)


Full Reconstruction of bc+

bc+

c+

pK

ECM Mb = 20 MeV

ECM = 4.5 MeV

Mc (GeV)

= 3.1 MeV


The Effect of Beam EnergyS

igm

a o

f M

c

(M

eV)

ECM2Mb (MeV)


The Effect of Beam Energy

ECM2Mb (MeV)

M

c

M

b(

MeV

)

Sig

ma

of

M

c (

MeV

)

ECM2Mb (MeV)

preparation of b scan jianchun wang syracuse university cleo meeting 04/13/02

Documents

b b events

b b crosssection

b b pair production

b threshold

b mesons

mev slide

jianchun jc wang13

jianchun jc wang4 events