hera-b physics results data of the year 2000 limited statistics 2.commissioning:
DESCRIPTION
Hera-B Physics results Data of the year 2000 limited statistics 2.Commissioning: trigger and detector not yet fully available (limited acceptance in x F ) Targets: C and Ti (partially simultaneously). General view of Hera-B. Rich. Trans. rad. det. vertex detector. ECAL. p. - PowerPoint PPT PresentationTRANSCRIPT
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 1
Hera-B Physics results
1. Data of the year 2000 limited statistics
2. Commissioning:trigger and detector not yet fully available(limited acceptance in xF)
3. Targets: C and Ti (partially simultaneously)
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 2
General view of Hera-B
vertex detector
outer trackerhi-Pt tracker
magnet (2 Tm)
inner trackermuon chambers (/h)
target
p
e
20 m
Rich
Trans. rad. det.
ECAL
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 3
Hera-B detector and trigger layout geared towards J/ :
1. Based on J/ e+ e- and J/ + - ;2. Good vertexing through Si- strips;3. e+ and e- in ECAL;4. + and - in Muondetector;5. Magnetic field for charge determination.
ECAL is also fine-grain photon detector.
Not used in this part of analysis:1. Rich2. Inner Tracker3. Trans. Rad. Detector
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 4
J/
J/ signal before cuts
+- inv. Mass:
J/ signal after cuts
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 5
e+ eInvariant mass spectrum
(| 1 - E/p| < 0.3)
No J/ signal …
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 6
beam e+
ECAL
e+
magnetic field
Bremsstrahlung recovery
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 7
eeInvariant mass spectrum
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 8
eeInvariant mass spectrum
(012) BR
(12) BR
(2) BR
before background subtraction after background subtraction
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 9
eeInvariant mass spectrum
with bremsstrahlung requirement
After background subtractionBefore background subtraction
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 10
J/ production
Hera-B has large xF (and good pT ) acceptance
xF xF
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 11
pT and xF distribution with e and sample:
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 12
Comparison with other experiments:
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 13
Fit ansatz: = a * (1 - |xF | )cd N(J/)
d xF
c = 6.2 + 0.6-
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 14
Energy dependence of exponent c
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 15
Energy dependence of width pT
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002
Nuclear effects:
Hera-B uses up to 88 different target wires simultaneously (in 2000: CC and Ti). Ti).
Most uncertainties cancel out: can easily measure nuclear exponent as function of xF or other parameters.
Important: goodaccep-tance in negative xF. (use W and C targets…)
2000
2002
16a
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 17
Rc =
NJ/ *
Nc
Identification of c through : M = M(l +l - ) - M (l +l - ) uncertainty in J/ mass essentially cancels:Mc
= (MJ/2 + 2E EJ/ – 2ppJ/ )
Mc = MJ/ = 0.877 MJ/
(Mc - MJ/ ) = -0.123 MJ/
MJ/
Mc
Ratio of J/ from c :
c Production
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 18
M-spectrum:c-signal on top of
combinatorialbackground (J/ -- )
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 19
ADC shift
Dependency of c reconstruction onECAL miscalibration
Nc (relative)
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 20
Dependency of Rc
on
upper limit of tracks:Jvaries, butRc
constant.
Rc
Nvds
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 21
Rc
Nclus
Dependency of Rc
on
upper limit of Ecal clusters:
varies, butRc
constant.
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 22
Comparison of with previous experiments
Final result : Rc
= 0.321 + 0.064stat + 0.035syst
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 23
Rc as function
of energy
Hera-B
p-A
-A
CSMp
p
NRQCD CEM
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 24
bb-cross sectionPrevious data
Factor 7
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 25
Method:• B = 10-12 s• B only long lived decay
into J/• at 920 GeV: ~ 1 cm• look for detached J/• normalize using known
cross section and measured number of J/and BR B J/
• no efficiency/trigger/…knowledge required(well, “almost not required”…)
Monte Carlo
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 26
Invariant di-muon mass spectrum after detached event selection
(incl. likelihood-fit).
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 27
Data Monte Carlo
Invariant Mass:for downstreamand upstreamevents
clear signal of detached J/
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 28
Decay length fit
signal = 1.0 +/- 0.3 (MC = 0.83 +/- 0.03)
backgr. = 0.39 +/- 0.11
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 29
Single cut optimizationon downstream bkgr.
Simult. cut optimizationon downstream bkgr.
Simult. cut optimizationon upstream bkgr.
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 30
Final result: (bb) = 32 +15 + 8syst nb/nucleon-12 stat -
Uncertainties:Reference J/ cross sect. 11 %Trigger simulation: 5 %prompt J/ product. models 2.5 %b prod. and decay model 8 %A-dep. ignored 1.7 %prompt J/ counting 5 %b lifetime error 1 % J/ e+e- 1 % +- background shape 20 % +- background fluct. 23 % e+e- background shape 14 % e+e- background fluct 11 %
Total 24 % – 33 %
-- Th. S. Bauer (NIKHEF) -- ECT -- 18. 6. 2002 31
Conclusion
• Results of 2000 limited in statistics(though competitive: (bb), Rc
)
• Hera-B offers good possibilities:• Simultaneous different targets
small relative uncertainties• large acceptance in - negativenegative - xF;• full event capability: PID, , …
• Improved detector (trigger) in 2002:high statistics expected