1 ISMD 2005I. Ripp-Baudot Heavy flavour production results from DØ Run II Isabelle Ripp-Baudot IReS Strasbourg / IN2P3 for the DØ collaboration International

ISMD 2005 I. Ripp-Baudot 1

Heavy flavour production Heavy flavour production results from DØ Run IIresults from DØ Run II

Isabelle Ripp-Baudot IReS Strasbourg / IN2P3

for the DØ collaboration

International Symposium on Multiparticles Dynamics

Kroměřίž, August 9-15, 2005


OutlineOutline

Tevatron Run II and the DØ detector

Spectroscopy :

- X(3872) J/ + -

- orbitally excited B mesons

- Bc J/ X

Cross-sections :

- inclusive (1S) differential cross-section

- tt production in the lepton+jets, dilepton and all-jets

Conclusion and outlooks.

-

Lots of c/b/t results from DØ

channels

focus on main spectroscopy / cross-sections results .


The Tevatron at FermilabThe Tevatron at Fermilab

Run II (since 2001) :

√s = 1.96 TeV

lumi > 1032 cm-2s-1

800 pb-1 recorded by DØ,160 to 370 pb-1 analysed.

2009 : Run I dataset x 40-80

Main injector & Recycleur

Tevatron

Chicago

p

p p

1.96 TeV

CDF

p

DØ

Total Luminosity (fb-1)

0

1

2

3

4

5

6

7

8

9

10/1/03 9/30/04 9/30/05 9/30/06 9/30/07 9/29/08 9/29/09

Design

Base

integrated luminosity (fbˉ¹)

2005 2007 2009

we are here4 fb-1

8 fb-1

2005: better than expected ! 2004

2003

2002

Design for 2005 Base for 2005


The DØ detectorThe DØ detector

Tracking system

Calorimeter

Muon chambers

Muon : excellent coverage ||‹2.0 + toroïdal magnet

Tracking system : 2 T solenoïdal B + 4 layers Silicon + 8 layers Fiber tracker. ||<3.0.

Calorimeter : liquid Ar with U/Cu absorber. Small segmentation x + good hermiticity. Coverage ||‹4.2


Heavy Flavour production in DØHeavy Flavour production in DØ

Trigger : crucial item !

3 levels

2.5 MHz 60 Hz

B physics : mostly (di)-mu trigger.

~ 3 t t / hours

~ 20.106

b b / hours

-

-

Considerable increase over the previous datasets. All states accessible : Tevatron is a unique place to study heavy b hadrons (Bc, Bs, b, B**) and the top quark.0

70 mb

7 pb

~ 7.106 events / s

even

ts /

10

MeV

/c2


spectroscopyspectroscopyresultsresults


Observation of X(3872) by DØObservation of X(3872) by DØ

DØ

Observation by DØ (PRL 93, 162002, 2004) :

data collected apr. 02 jan. 04 ~ 230 pb-1

Using DØ dimuon trigger.

+-+- vertex reconstructed.

First observation by Belle in 2003 in J/ + - decay channel.

--

Spectroscopic puzzle : D0-D*0 hadronic resonance, ccg-hybrids, unknown charmonium state, diquark-antidiquark state, … ?

X(3872) J/ + -

522 ± 100 X(3872) candidates.

M(X-J/) = 774.9 ± 3.1(stat)

± 3.0(syst) MeV/c2

At Tevatron : B decay + direct production.


Properties of X(3872)Properties of X(3872)

DØ

pT ›

15

GeV |y|

‹ 1

(2S) with same decay channel = good benchmark for comparison with X(3872).

Data separated according to production and decay variables.

Conclusion : no significant differences between X(3872) and (2S).

lxy ‹

0.0

1 c

m

isola

tion =

1

Helic

.

‹ 0

.4

Future investigations :

- Search for radiative decays and other final states with neutrals in progress.

- Lifetime measurement.

- Search for charge conjugate X+ J/ + 0

- Quantify prompt production w.r.t. through decay in progress.

Helic

ity

‹

0.4

Presented by Belle Summer 2005 : quantum number C=+1 established, X J/ and + - 0 J/ observed with more than 4 agreement with D0D*0 resonance prediction.


Reconstruction of orbitally Reconstruction of orbitally excited Bexcited B

Reconstruction of L=1 B states : the two narrow B**, B1 and B* , decaying to B(*) .

DØ DØ

B± J/ K± Bd J/ K*0(892) Bd J/ Ks0

7217 ± 127 2826 ± 93 624 ± 41

Precise predictions for B** properties by HQET interesting lab to test the validity of heavy quark symmetry and help further development of NPQCD.

These B hadron candidates + 1 additional track originating from interaction point : B0 ±, B± .

Exclusively reconstructed B mesons in hadronic decay channels allow measurement of B** properties. Reconstruction with data collected 2002 2004 ~ 350 pb-1 (DØ dimuon triggers).

First observation of B1 and B* as two separate states, with a significance of 7.

2

d

( ) ±

DØ

2

-


Study of BStudy of B****

- Expected decays : Br(B1 B* ) >> Br(B1 B ), Br(B* B* ~ Br(B* B ),

with B* B distribution of M = M(B) – M(B) should reveal 3 peaks, but since

M(B*) – M(B1) << detector resolution, the first 2 peaks are

unresolved.

- Expected widths : 1 ~ 2 set 1 = 2 in the fit.

2 2

DØ

2

B* B 2

2/NDF = 54.3/50

M(B1) = 5724 ± 4 (stat) ± 7 (syst) MeV/c2

M(B*) – M(B1) = 23.6 ± 7.7 (stat) ± 3.9 (syst) MeV/c2

1 = 2 = 23 ± 12 (stat) ± 9 (syst) MeV/c2

2

Future : increase in stat. will

allow the precise measurement of B** production and decay properties.

Fit results :

B* B* 2

- Since M(B+**)-M(B0**) << mass resolution, B+** ~ B0** = B**.d du u

B B* 1


Observation of BObservation of Bcc

Heaviest B meson ground state, made of two heavy quarks.

Test of heavy quark fragmentation and hadronization.

Previously observed by CDF Run I but up to now limited statistics.

Reconstructed channel : Bc J/ X - 3 muons easy to trigger on.

- less background than Bc J/

- limited mass precision due to escaping .

Using 210 pb-1 of DØ data : 95 ± 12(stat.) ± 11 (syst.) Bc signal candidates

significance > 5

DØ preleminary

Background composition checked with data and MC simulation :

1) Prompt J/ + common vertex with decay-in-flight to , punch-through calo.

2) J/from B + decay-in-flight to or punch-through in the same jet or elsewhere in event.

(@ 5.95 GeV/c2)


Properties of BProperties of Bcc

Simultaneous mass/lifetime fit :

+0.14

-0.13

+0.123

-0.096

mBc = 5.95 (stat) ± 0.34(syst) GeV/c2

Bc = 0.448 (stat) ± 0.121(syst) ps

Under investigation : - establish Bc pT spectrum to compare with phenomenological predictions.

- smaller systematics errors.

- reconstruct exclusive Bc J/

heavy flavour background

prompt background

signal @ 5.95 GeV/c2

Phenomenological predictions :

m(Bc) ~ 6.4 GeV/c2

(Bc) ~ (D meson) ~ 0.3 to 0.5 ps.

Mass hypothesis (GeV/c2)

-2lo

gL


cross-sectioncross-sectionresultsresults


InclusiveInclusive(1S) differential (1S) differential cross-sectioncross-section

DØ measurement (PRL 94, 232001, 2005) :

data collected june 2002 sept. 2003

~ 159 pb-1.

- Reconstruction of (1s) + - as function of

pT() and in 3 y = ½ ln ranges :

0 < |y| < 0.6

0.6 < |y| < 1.2

1.2 < |y| < 1.8

DØ

DØ

4 GeV/c < pT() < 6 GeV/c

|y| < 0.6

1.2 < |y| < 1.8Hypothesis : (1S) are produced

unpolarized (CDF Run I measurement). Sensitivity checked < 4 % in all pT bins.

new !

E+pzE-pz


InclusiveInclusive(1S) differential (1S) differential cross-section cross-section (cont.)(cont.)

DØ

Conclusion :

- first measurement in the forward region.

- agreement with CDF Run I measurement.

- reasonable agreement with theoretical predictions [Berger, Qiu, Wang, PRD 71 (2005)].

- systematics limited : no need to increase stat. up to now.

Measurement for |y| < 0.6 :

(1S) x Br((1S)+-) = 732 ± 19(stat) ± 73(syst) ± 48(lumi) pb

new rapidity ranges

Future : DØ measurement of (1S) polarization in progress.


tt cross-sectiontt cross-section--

Top quark was discovered by CDF and DØ at Tevatron in 1995. Largest known mass ( new 2005 : 172.7 ± 2.9 GeV/c2) and lifetime (~ 5.10-25 s) shorter than hadronisation time (~ 10-23 s) decays as a free quark.

At Tevatron, top mainly produced by pair via strong interaction.

fully hadronic

hadr + jets

lepton + jets

lep

ton

+

jets h

ad

r +

jets

dilepton

+ ℓ

+

ℓ

---

-

- - - -

e-

e+ +

-

-

+

ud

cs

csud

-

-

- -

- BR ~ 45 % large statistics

- 6 jets

- large multijet background with poorly known cross-sections

- BR ~ 5 %

- 2 jets

- clean channel

- low statistics

no +X analysis so far

- BR ~ 30 %

- 4 jets

- optimum stat/background

In all channels : At least 2 bjets possibility to use b-tagging to improve signal/background.

all jets

ℓ-jets

ℓ-ℓ


tt cross-section tt cross-section (cont.)(cont.)--

jet multiplicity

jet multiplicity

background control

tt measurement

one tagged b-jet

two tagged b-jets


Conclusion and outlooksConclusion and outlooks

Studies of beauty and top production are important tests of perturbative QCD.

Tevatron is a unique place to study top and several B properties.

DØ takes advantage of its muon trigger with excellent coverage, and its new tracking system.

It benefits furthermore from the very high statistics provided by the Tevatron : about 200 to 400 pb-1 analysed up to now. Some analysis still limited by stat, but statistics also allow systematics improvements. Already 1 fb-1 delivered, 4-8 fb-1 expected around 2009 lots of good results to come.


Backup slidesBackup slides


InclusiveInclusive-tagged jet cross--tagged jet cross-sectionsection

Previous measurements of heavy quark production at the Tevatron showed discrepancies with theoretical predictions, now understood after evolution of both theory and experimental measurements.

Focus on b-jets rather than b-quarks directly observable.

294 pb-1 sample of mu-tagged jets in the central region |y| < 0.5 differential cross-section as a function of jet ET. Very high jet Et (> 50 GeV).

-tagged jet : have a within the jet cone and the production vertex occurs within a cylinder of r=10 cm centered on the beam axis to get rid of contamination from and K decay.

# event in each pT bin = pT

Trigger PV jet

purity

measured

1) missed from B decay pT resolution degradation

2) detector resolution taken into account by unsmearing : observed jet pT true jet pT

Consider only the top of the detector to avoid selecting fake muons (punch-through the calorimeter) : less muon detector layers on the bottom because of the detector’s support.

d

dpT


InclusiveInclusive-tagged jet -tagged jet cross-section cross-section (cont.)(cont.)

Systematics :

- fraction of heavy flavours (pT independent)

- jet energy scale (pT dependant)

Future : extract exclusive b fraction.

Remove light quarks contribution : use the simulation to determine the fraction of -tagged jets originating from a heavy quark (b or c).

DØ

Comparison to theory predictions :

1) PYTHIA LO approximation

2) NLO calculation for inclusive jet calculation pT dependent fraction of jets that are -tagged (PYTHIA)

Documents

1 ISMD 2005I. Ripp-Baudot Heavy flavour production results from DØ Run II Isabelle Ripp-Baudot IReS Strasbourg / IN2P3 for the DØ collaboration International