February 2006 Kin Yip 1

Lifetime Difference (Lifetime Difference ( = 1/ = 1/ ) in the B ) in the Bs s SystemSystem Lifetime Difference (Lifetime Difference ( = 1/ = 1/ ) in the B ) in the Bs s SystemSystem

Avdhesh Chandra, UCR

Kin Yip, BNL

Daria Zieminska, IU

D Winter Physics WorkshopFebruary 21, 2006

February 2006 Kin Yip 2

Old (PRL 2005) and New Analyses

PRL 95, 171801 (2005) ~0.45 fb-1

Triggers v13 and lower1- and 2-muon triggers

unbiased in cReco p14

1-angle analysis~500 signal events

Winter 2006 ~0.9 fb-1 (?) [ D Note 4810 ]

Triggers v14 and lower1- and 2-muon triggers, unbiased in c and track pT

(173 trigger names)

Data sample: CSskim p17fix + p17.09 (4%) (SKIM_2MU)

Compared to 2005 PRL • Improved track energy loss • Rematched muons• “adaptive” vertexing• Same kinematic cuts, slightly tigther quality cuts

3-angle () analysis~1000 signal events

CKM Matrix and Unitarity triangle

1)1(

21

)(21

23

22

32

AλiηρAλ

Aλλλ

iηρAλλλ

‘bd’ (THE unitary triangle) Large effort in B physics Mainly at B factories

’bs’ (A ‘squashed’ unitary triangle)

s, small in SM

Interesting to check how small/big s really is.

Currently: Tevatron domain

Relates quarkmass and weak eigenstates

SM: CP-violating processes solely related to one phase in CKM.

tbtstd

cbcscd

ubusud

VVV

VVV

VVV

(1,0)

(0,0)

()

*

*

cbVcdV

tbVtdV

*

*

cbVcdV

ubVudV

February 2006 Kin Yip 4

Bs System and CP violation

cbcs

cbcs

tbts

tbtsi

VV

VV

VV

VVec CP violating

weak phase

In Standard Model, λ (0.03), very small. Much larger measurement of a striking signal of new physics in

Bs – Bs mixing.

oddeven

oddeven

B)2

1(B)

2

1(B

B)2

1(B)

2

1(B

H

L

ss

ss

ii

ii

ee

ee

m = MH ML > 0; = L - H (> 0 in Standard Model)

Any dependence on mt cancels in untagged samples.

s SM)

February 2006 Kin Yip 5

Untagged Bs Decay

Bs J/, Pseudoscalar Vector Vector decay

Three waves: S, P, D, or ┴

Both CP-even and CP-odd present, but separated in angular distributions

S, D (Parity, CP even) :linear combination of

P (Parity, CP odd) : ┴

R ┴ ┴(t=0)|

February 2006 Kin Yip 6

Bs Lifetime Difference

• We measure TWO distinct lifetimes (or, equivalently, and by fitting time evolution and angular distributions in untagged Bs Jdecays.

• If CP is conserved, they can be interpreted as the lifetimes of the two Bs mass eigenstates.

• We discuss the sensitivity to a free CP violating angle

D0 p17fix/p17.09

History:

CDF (PRL 2004) fit used 3 angles, 203 events

D0 (PRL 2005) used 1 angle, θ, 513 events

Nsignals = 978 45

February 2006 Kin Yip 7

Some selection cuts

Bs candidate mass

J/ candidate mass

Non-J/ meson mass

Bs pT

J/ pT

pT

J/, 2

K± pT

SMT hits each track (incl. fdisk)

SMT+CFT hits on track

B candidate decay length error

5.0 < M(J/,) < 5.8 GeV

2.9 < M(+,-) < 3.3 GeV

1.01 < M(K+,K-) < 1.03 GeV

> 6.0 GeV

> 4.0 GeV if || < 1.0

> 1.5 GeV

< 10.0

> 0.7 GeV

>1

>7

< 0.006 cm

Total number of Bs J candidates: 21380 (PRL 2005: 9699)

CSG p17fix + p17.09

February 2006 Kin Yip 8

Data

February 2006 Kin Yip 9

Untagged Bs Decay Rate in Time & Angles

Arg[A||(0┴andArg[A0(0)A┴(0)] are CP-conserving strong phases

No dependence on mt

correction for acceptances, kinematic cuts

Detector Acceptance (MC & data)

G(cos ) = 1 + Bcos2 + Ccos4

H(cos ) flat distribution

F() = 1 + J cos(2) + K cos2(2)

February 2006 Kin Yip 11

Maximum Likelihood FitSimultaneous fit to mass, proper decay length and 3 angles

using an unbinned maximum log-likelihood method

30 parameters: 1 fsig = signal fraction

2 signal mass, width

3 A , |A0|2-|A|||2, 1 strong phase

1 c = c / , = (LL+ HH) /2) /2

1 = = LL - - HH

3 bkg mass (1 prompt, 2 long-lived)

1 (ct ) scale

6 bkg ct shape

4 bkg transversity (2 prmpt + 2 long-lived)

4 bkg angle φ (2 prompt + 2 long-lived)

2 bkg angle ψ (1 prompt + 1 long-lived)

2 bkg “interference” (1 prompt + 1 bkg)

])1([1

i

bcksig

N

i

i

sigsig ff FFL

set

February 2006 Kin Yip 12

Full (chain) MC TestInput: (close to PRL 2005 results)

cL = 370 µm cH = 460 µm|A┴| = 0.4 with ~9K events (~10 current stats)

February 2006 Kin Yip 13

Data:Fit projections in signal regions

transversity)

February 2006 Kin Yip 14

Fit projection (lifetime)

All events

Background mass region

Signal mass region

February 2006 Kin Yip 15

Results (3-angle fit)

February 2006 Kin Yip 16

Cross-check: 1-angle fit

This analysis PRL (2005)

February 2006 Kin Yip 17

Comparisons:

D ’06 – errors statistical only

0.140.06

1.580.09

0.220.13

February 2006 Kin Yip 18

Systematics

One “outlyer” treat its effect as systematic uncertainty Event Run #: 210344 Event #:23385781 unlikely signal or background Signal: mass 2.3 from peak, lifetime 8.5 x mean Bkg: 10.2 x mean for “right slope long”

1 - 2

February 2006 Kin Yip 19

Sensitivity to CP violation

So far, we have assumed CP to be conserved, i.e., no interference between CP-even and CP-odd terms, and

the two physical Bs states, L and H, are orthogonal

CKM (Standard Model) : λ 0.03

Allowing for a free requires an assumption on strong phases 1 2,our fit does not converge with all 3 phases free

With 1 free and 2 = 0, we obtain = -0.9 ± 0.7CP-violating angle consistent within statistical uncertainty of ± 0.7.

February 2006 Kin Yip 20

Summary

NNewew results based on X2

New analysis based on ~1 fb-1 data

Statistical uncertainty on the CP-violating angle 0.7

Bd J/ K analysis is in progress