B Production and Decay at DØ

Brad Abbott

University of Oklahoma

BEACH 2004

June 28-July 3

B physics at DØ• Will be presenting latest results on:

– D**

– B**

– Bs

(1S) production

– X(3872)

• Keys to DØ B physics program– Muon system and trigger

– Silicon vertex detector and fiber tracker

L= 115 – 250 pb-1

SMTSMT

SMT

Muon System and Tracker • New forward muon system with ||<2 and good shielding • 4-layer Silicon and 8 doublet-layer Fiber Trackers in 2 T

magnetic field

Observation of B D** X

• D** are orbitally excited D meson states

• In heavy quark limit– Two narrow states (D-wave)

– Two broad states(S-wave)

• Search for narrow states via– D0

1(2420) D*+ -

– D*02(2460) D*+ -

D0 sample

• D10 and D2*0 observed in

several experiments, most recently by BaBar/Belle in B- D**0 -

• DØ is studying D10 and

D2*0 in B semileptonic

decays

• Start with B D0 X (D0 K)

D* sample

• Add a pion (charge correlated with the muon) with PT>0.18 GeV

D**

• Measure invariant mass of D*- + system

• See merged D10(2420)

and D2*0 (2460)

Wrong sign combinations

Interference effectsTwo interfering Breit-Wigner D** states with mass/width as measured by Belle (no resolution effects included)

Work in progress to extract separate amplitude for eachstate and relative phase of interference.

Branching ratio• Take experimentally measured number of D1

0 and D2*0 : N(D1)+N(D2*)=523 40

• Measure branching ratio of B D**(narrow) X, normalizing to known branching ratio (B D*+ X)

• Br(B {D10,D2*0} X • Br({D1

0,D2*0} D*+ -) = 0.280 0.021(stat) ± 0.088 (sys) %

• Compare to LEP measurement of total D** Br (B D*+ X) = (0.48 0.10)%

• ~ half the rate through narrow states

Future measurements

= 0.4-0.7 predicted by HQET

World average =0.4 ± 0.15

DØ can measure:• R• Br(B D1X )• Br(B D*2 X)• Interference effects• Helicity

B**

• Heavy quark symmetry predicts 4 B*J states JP = 0+, 1+ , 1+ , 2+

• Parity and angular momentum require B*J to decay to B* or B

• B** provide a good test of heavy quark symmetry• Many properties of the B** unknown• Large B cross section at Tevatron allows for

precise measurements with large statistics

B**

• Search for B**d B+ -

B+ J/ K+ • Allows one to charge

correlate the pion and the B to reduce combinatoric background

115 pb-1

PDG Average 5.698 0.008 GeV

Additional Channels

• Are adding in more decays to increase statistics

• B**+ Bd

– Bd J/ K*

– Bd J/ KS

• With increased statistics should be able to resolve the narrow B** states.

Bd,s

• Forbidden at

Tree Level in SM

BR(Bd l+l-) BR(Bs l+l-)

e (3.4 ± 2.3) 10-15 (8.0 ± 3.5) 10-14

(1.5 ± 0.9) 10-10 (3.4 ± 0.5) 10-9

(3.1 ± 1.9) 10-8 (7.4 ± 1.9) 10-7

Theoretical predictions

Experimental limits at 90% CL

BR(Bd l+l-) BR(Bs l+l-)

e < 5.9 10-6 < 5.4 10-5

< 1.5 10-7 < 5.8 10-7

< 2.5 % < 5.0%

Bs in SUSY(Two Higgs-Doublet Model)

• BR depends only on charged Higgs mass and tan

• BR increases as tan4 (tan6) in 2HDM (MSSM)

• R parity violating models can give tree level contributions

Dimuon Data sample

Cut optimization

• Signal box is blinded

• Use a random grid search optimizing the ratio

Ba 2/

= reconstruction efficiency of signal MCB= expected background extrapolated from sidebandsa = number of sigmas corresponding to confidence level (set to 2 for this analysis, corresponding to ~ 95% CL

(Following proposal fromG. Punzi physics/0308063 Test of hypothesis and limits)

Discriminating variables• Isolation of the muon pair

• Opening angle between momentum vector of pair and vector pointing from primary vertex to vertex

• Decay lengthBox not opened yet180 pb-1

Expected upper limit

• Since box not opened, calculate expected upper limit

• Expected signal normalized to B+J/K+

• Expect 7.3 ± 1.8 background events in signal region

• Current expected limit using Feldman-Cousins:

Br(Bs ) < 1.0 10-6 @ 95% CL (stat + sys) Reoptimization still in progress.

Further improvements expected

(1S) Production• Measuring the (1S) production cross section

provides a test of our understanding of the production mechanism of heavy quarks

• Extend measurement of (1S) cross section to rapidities of 1.8

• Color octet model predicts an increase in transverse polarization with increasing PT

(Measurements so far are inconclusive)

Analysis• Measure the (1S) cross-section as a function

of PT in three rapidity regions

0< |y| <0.6 0.6<|y|<1.2 1.2<|y|<1.8

Signal fit to 3 Gaussians (1S), (2S), (3S) Background: 3rd order polynomial

m((2/3S) = m((1S) + mpdg((2/3S)- (1S))((2/3S) = ((1S) + m (2/3S)/m((1S))* ((1S))

5 parameters: m, (1S)Number of (1S), (2S), (3S)

Normalized cross section

159 pb-1

Normalized Cross section

Normalized cross section

• Normalized cross section shows little dependence on rapidity

• Good agreement with published results

• Absolute cross section nearly ready

• Next: Polarization measurement

X(3872) J/ + -

• First observed by Belle B+ K+ X(3872) decays• Signal confirmed by CDF, DØ and BaBar• Nature of X(3872) unknown• Theories include:

– Another charmonium state– D D* molecular state

• Since the X(3872) lies very close in mass to the Ψ(2S) charmonium state, and has a common decay mode (X J/, we compare production and decay properties of these two states through this decay mode

X(3872)

M=774.9 ± 3.1 (stat) 3.0 (sys) MeV

522 ± 100 X candidates

Significance = 5.2

230 pb-1

• Separate data into different regions

• Compare (2S) yield to X yield in different regions

• Study production and decay characteristics

• a) PT > 15 GeV• b) |y| <1• c) |cos()| < 0.4• d) decay length < 0.01 cm• e) isolation=1• f) |cos ()| < 0.4

(: boost one of the pions and the X(3872) into dipion rest frame.

is the angle between them)

• To within uncertainties, production of X(3872) found to be consistent with the production of the Y(2S) I.e producted both directy and via B decays,

• Future: look for radiative decays and charge analog of X

Compare2||))3872((

1||))3872((

yXN

yXN

2||))2((

1||))2((

ySN

ySN

Submitted to PRL: hep-ex/0405004

Summary

• Observation of B D** X

• Observation of B**

• Sensitivity to Bs

• Normalized Upsilon(1S) Cross section

• Observation of X(3872)

• Many new analyses on the way