Andrei Nomerotski (Oxford)1

Andrei Nomerotski (Oxford/Fermilab) ICHEP 2006, 29 July 2006

B Hadrons at DZero

Outline B hadrons at Tevatron and DZero Excited B** mesons First Evidence of Bs** First observation of BsDs(2536)X

Lifetime of B Baryons

Andrei Nomerotski (Oxford)2

Tevatron Excellent performance in

2005-2006 : 1.2 fb-1 on tape per experiment

Successful shutdown ended in June – detectors upgraded

Expect 4-8 fb-1 by the end of Run2 in 2009

Results presented here use 1 fb-1

Andrei Nomerotski (Oxford)3

B Hadrons at Tevatron Produced strongly at Tevatron

crossection x10000 wrt B-factories

…but large background Tevatron has access to B hadron species

inaccessible in other colliders modulo recent (5S) dataset at Belle gives access to Bs

mesons

Long lifetime and heaviness of b quark significant theoretically and experimentally

Andrei Nomerotski (Oxford)4

DZero Detector Spectrometer : Fiber and Silicon Trackers in 2 T Solenoid Energy Flow : Fine segmentation liquid Ar Calorimeter and Preshower Muons : 3 layer system & absorber in Toroidal field Hermetic : Excellent coverage of Tracking, Calorimeter and Muon Systems

SMT H-disks SMT F-disks SMT barrels

Andrei Nomerotski (Oxford)5

DZero Detector in Collision Hall

Andrei Nomerotski (Oxford)6

Light – Heavy Quark Mesons Light – Heavy quark mesons are hydrogenic

atoms of QCD Heavy Quark limit static colour field & decoupling of

light degrees of freedom Light quarks characterized by their total angular

momentum jq = sq + L

jq is combined with SQ to give total angular momentum

SQ and jq are separately conserved

In Heavy Quark Limit, each energy level has pair of degenerate states :

Qs

Lsj qq

Q qJ s j

jq=1/2 J=0 B

J=1 B*

L=0jq=1/2 J=0,1 B0

*, B1*

jq=3/2 J=1,2 B1, B2*

L=1 states, also known as B**

Andrei Nomerotski (Oxford)7

B** Spectroscopy

B1 and B2* decay through D-wave narrow resonances

B0* and B1* decay through S-wave wide resonances, difficult to distinguish from phase space

Andrei Nomerotski (Oxford)8

Excited B Analysis Search for narrow states decaying

to B+(*) B1 B*+-; B*+ B+ B2

* B*+-; B*+ B+ B2

* B+-

Reconstruct B+ J/ K+ with J/

For each B hadron look for additional track with

PT> 0.75 GeV Correct charge correlation

(B+- or B-+) Since B** decays immediately

after production, track was required to originate from primary vertex.

~16K B+ J/ K+

μμ

K

π

B

Primary vertex

Andrei Nomerotski (Oxford)9

Excited B Results Form mass difference

M=M(B)-M(B) Three peak structure

Direct decay B2* B+ B2* B+* with B+* B+

E46 MeV and since is not reconstructed, expect a peak separated from direct peak by energy

B1 B+* with B+* B+ B1 B is forbidden by

angular momentum and parity conservation

Results: M(B1)=5720.8 ± 2.5(stat) ± 5.3 (sys) MeV

M(B2*)-M(B1)= 25.2 ± 3.0(stat) ± 1.1 (sys) MeV

1=2= 6.6 ± 5.3(stat) ± 4.2 (sys) MeV

Andrei Nomerotski (Oxford)10

Excited B Results

0.513 ± 0.092(stat) ± 0.115(sys)

0.545 ± 0.64(stat) ± 0.071 (sys)

0.165 ± 0.024 (stat) ± 0.028 (sys)

)(

)((*)*

2

**2

BBBR

BBBR

)(

)((*)

*1

BBBR

BBBR

J

)(

)( 0

BbBR

BBbBR J

First measurement of production rate, world’s bestmass measurement

Andrei Nomerotski (Oxford)11

Bs2*: Excited Meson

States similar to B1 and B2* should exist in (bs) system, i.e. there should be Bs1 and Bs2

* mesons

Almost no information exist on these objects: few claims of indirect observation at LEP by OPAL and DELPHI

Like for normal B**, there should be narrow Bs1 and Bs2* states

Due to the isospin conservation, possible decays are: Bs1B* K

Bs2*B K, Bs2B* K

)s(b

Andrei Nomerotski (Oxford)12

Search for Bs2*

Search for excited states decaying to B+K - very similar to B** search

μμ

K

K

B

For each B hadron an additional track

PT > 0.6 GeV Charge opposite to

charge of B+

Track was required to originate from primary vertex

Kaon mass assigned to track

Primary vertex

Andrei Nomerotski (Oxford)13

M(B*s2) = 5839.1 ± 1.3 MeV

Mass difference M=M(B+K-)-M(B+)-M(K-)

Significance of signal > 5

Bs2* Results

Wrong sign charge correlations showsno evidence of a peak

MC B** decaying to B(*) but reconstructed as B+K- show noevidence of a peak. First Direct observation of B*s2

Andrei Nomerotski (Oxford)14

Where is Bs1?

Suppose that M(Bs2*) – M(Bs1) M(B2*) – M(B1),

Take M(B2*) – M(B1) = 26 MeV from our B** results,

We conclude that decay B1sB* K should be prohibited, or at least strongly suppressed, because:

M(Bs1)M(Bs2*) – 26 MeV= 5813 MeV < M(B*)+M(K).

It means that the only possible decay of Bs1 is EM decay:

Bs1Bs(0)

Andrei Nomerotski (Oxford)15

Look for narrow (L=1,jq=3/2,JP=1+) in (2536)Ds1

KDDD

KKD2536D

X2536DBb

SSs

sS

00*

00*1

10

,

)(

)(

Muon plus 5-Track final state

1 fb-1

82130D* candidates In 0.142-0.149GeVmass difference window

Orbitally Excited Ds1(2536) Meson

Andrei Nomerotski (Oxford)16

43.8±8.3 D±s1(2536) candidates 5.3 σ significance

2535.7±0.5(stat)±0.6(sys) MeV2535.34±0.31 PDG

0

Reconstruction of Ds1(2536) Meson

Andrei Nomerotski (Oxford)17

Br measurement

Measure product Br

Assuming

To be compared to theoretical predictions for

Andrei Nomerotski (Oxford)18

b Lifetime

Lightest b baryon (udb) Access to various important topics

Spin role in heavy hyperons (polarization) CP violation Exotics : T violation or other new physics in

Lifetime : Tests of HQE Theory in b baryons

Controversy between experimental and theoretical results seems to disappear as more precise measurements and calculations become available

At the same time the CDF most recent measurement is considerably above the world average

llb

Andrei Nomerotski (Oxford)19

Measurement of b Lifetime in b J/

174 ± 21 candidates reconstructed in J/decay mode

Andrei Nomerotski (Oxford)20

Measurement of b Lifetime in b J/

B) = 1.298 ± 0.137(stat) ± 0.050(syst) psB)/) = 0.870 ± 0.102(stat) ± 0.041(syst)Main systematics from background modelling and from

contamination from B mesons

D0 Run2 preliminary, 1fb-1

this result

Andrei Nomerotski (Oxford)21

Summary

Good progress in understanding of excited heavy flavour mesons at Tevatron with 1fb-1 dataset Observation of B1 and B2* as two separate peaks, measurement

of masses First direct observation of Bs2* with > 5 significance, precise

mass measurement of Bs2*

First observation of BsDs(2536)X decay and measurement of its Br

Updated B lifetime measurement – agrees with world average

4-8 fold increase of statistics before 2009 with upgraded detectors