Post on 29-Mar-2015
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
ISMD 2005 I. Ripp-Baudot 2
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 .
ISMD 2005 I. Ripp-Baudot 3
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
ISMD 2005 I. Ripp-Baudot 4
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
ISMD 2005 I. Ripp-Baudot 5
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
ISMD 2005 I. Ripp-Baudot 6
spectroscopyspectroscopyresultsresults
ISMD 2005 I. Ripp-Baudot 7
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.
ISMD 2005 I. Ripp-Baudot 8
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.
ISMD 2005 I. Ripp-Baudot 9
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
-
ISMD 2005 I. Ripp-Baudot 10
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
ISMD 2005 I. Ripp-Baudot 11
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)
ISMD 2005 I. Ripp-Baudot 12
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
ISMD 2005 I. Ripp-Baudot 13
cross-sectioncross-sectionresultsresults
ISMD 2005 I. Ripp-Baudot 14
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
ISMD 2005 I. Ripp-Baudot 15
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.
ISMD 2005 I. Ripp-Baudot 16
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
ISMD 2005 I. Ripp-Baudot 17
tt cross-section tt cross-section (cont.)(cont.)--
jet multiplicity
jet multiplicity
background control
tt measurement
one tagged b-jet
two tagged b-jets
ISMD 2005 I. Ripp-Baudot 18
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.
ISMD 2005 I. Ripp-Baudot 19
Backup slidesBackup slides
ISMD 2005 I. Ripp-Baudot 20
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
ISMD 2005 I. Ripp-Baudot 21
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)