prospects for x(3872) detection at panda jens sören lange, martin galuska, thomas geßler, wolfgang...
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Prospects for X(3872) Detection at Panda
Jens Sören Lange, Martin Galuska, Thomas Geßler, Wolfgang Kühn,Stephanie Künze, Yutie Liang, David Münchow, Björn Spruck,Matthias Ullrich, and Marcel Werner
II. Physikalisches Institut, Justus-Liebig-Universität Gießenfor the PANDA Collaboration
12th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon05/31-06/04, 2010College of William and MaryWilliamsburg, Virginia
This talk:
only MC
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The X(3872)
A charmonium(-like) state found inX(3872) → J/ + −
Observation of decay into J/ → C=+1
interesting properties:breaks isospin in the decaysJ/(! + −), J/(! + − 0)→ is it charmonium?
Within m < 1 MeV of the DD* thresholdS-wave molecular state?
(to be) investigated at Belle, BaBar, CDF-II, D0BES-III, Belle-II
However:width is unknown<2.3 MeV (Belle)
Belle
Belle, Phys. Rev. Lett.91(2003)262001
CDF-II, Phys. Rev. Lett.93(2004)072001
D0, Phys. Rev. Lett.93(2004)162002
BaBar, Phys. Rev. D71(2005)071103
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Charmonium Production inpp collisions
X(3872) has C=+ In e+e− collisions only JPC=1–− can be produced directly
inpp collisions any quantum number
Resonance scan with a cooled anti-proton beam: the width of the X(3872) could be measured
! Panda Experiment at FAIR
2 gluons: 0−+, 0++, 2++
3 gluons: 1−−, 1+−
J=0,2
J=1
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GSI todayGSI todayFuture facilityFuture facility
2R=1.084 km
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HESR (High Energy Storage Ring)
PANDA
High intensity mode
•
• (stochastic cooling)
High resolution mode
•
• (e– cooling)
High intensity mode
•
• (stochastic cooling)
High resolution mode
•
• (e– cooling)
Internal targets• • Pellets• Cluster jet• Nuclei: Be, C, Si, Al
Internal targets• • Pellets• Cluster jet• Nuclei: Be, C, Si, Al
p 1011
410p/p
510p/pp 1010
-1-232 scm102L
' 2 x 109 J/ per year
For Anti-Protons
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The Pellet Target
Here: WASA Targetd=25 mfall speed ¸ 60 m/s
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Example of Charmonium Width Measurements
(J/) = 99 § 12 § 6 keV (´) = 306 § 36 § 16 keVby FERMILAB E760 and E835
beam momentum resolution p/p‚ 2 £ 10−4
→ s FWHM resolution 0.5 MeV
£ BR (J/) ' 630 nb
30
25
20
15
10
5
Even
ts/L
um
inosit
y
(nb
)
1
2
3
4
5
Even
ts/L
um
inosit
y
(nb
)
J/
´
Phys. Rev. D 47(1993)772
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Panda Experiment
MVD Micro Vertex DetectorTPC Time Projection ChamberEMC Electromagnetic Calorimeter
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PandaRoot Framework Simulation,
DigitizationReconstruction,Analysis
43,000 geometry volumes ¸ 400,000 lines of C++ code Transport engines:
Geant3, Geant4, FLUKA Event Generators:
EvtGen, DPM, PYTHIA, UrQMD ¸ 20 Linux platforms Improvements since
Panda Physics BookarXiv:0903.3905 X(3872) simulations for the 1st time field maps track finder and track fitter final state radiation
PHOTOS, Comp. Phys. Comm. 79(1994)291-308
For further informationhttp://panda-wiki.gsi.de/cgi-bin/view/Computing/PandaRoot
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PandaRoot Implementation of relevant Detectors
MVD
120 pixel modules100x100 µm2 pixel size~107 readout channels
400 strip modules~0.5 m2 active area7x104 readout channels
TPC
135 padrows135,169 pads of 2x2 mm2
EMC
~17,200 crystalsPbWO4 (radiation hard, fast decay~6 ns)28 X0
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11Sören Lange | X(3872) at Panda
Estimated Rates for X(3872) Formation at Panda pbeam=6.99100 GeV/c Baseline assumption: peak = 50 nb If X is a loosely bound DD* state
Chen, Ma, Phys. Rev. D77(2008)097501cross section estimate ·443 nb
Branching fractions of decays of X(3872) into DD* : J/ + − : J/ assumed as 9:1:0
J/ ! e+ e− and + −
BR ' 6% each Reconstruction efficiency ' 50%
(track reconstruction efficiency for low momentum § )! 250 pb
high resolution mode p/p =10−5 is low luminosity mode: L=2£1031 cm−2 s−1
duty factor = 50% L int= 0.86 pb−1/day 20 points for resonance scan
2 days/point Yield ' 215 events of X! J/ + − per day at peak
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12Sören Lange | X(3872) at Panda
X(3872)! J/ + – Event, PandaRoot Simulation
Beampipe
Beampipe
Targetpipe
Targetpipe
e§
e§
§
§
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X(3872) Events in Panda MVD+TPC PandaRoot Simulation
BeampipeInteraction
XYZ coordinates / cm XYZ coordinates / cm
XYZ coordinates / cm
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Comparison of e+ e− and + − final states
CombinatorialBackgroundonly
2-particle invariant mass
Radiative Tail due toFinal state radiation(PHOTOS)
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Particle Indentification (PID)
Using EEMC/ptrack (requires track-cluster matching)
EEMC is deposited cluster energy
Ptrack is reconstructed track momentum (TPC + MVD)
´ → J/ + −,no J/ decay
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Example MC Results for X(3872)! J/ + −
2-particle invariant mass 4-particle invariant mass
X(3872)J/
withoutPID
withPID
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Variation of Angular Distributions
Panda is fixed target experiment Negligible effect on reconstruction efficiency (<1%) ! Lorentz boost dominates acceptance
phasespacevector → vector+ pseudoscalar+ pseudoscalar
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Kinematic Fit: Vertex Constraint and Mass Constraint
Example:
reference mode
´ ! J/ + –
No fit No fit
Fit Fit
J/ ‘
J/ ‘
Constraint
m'3 MeV
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Background: pp ! 2 + 2 −
COMPILATION OF CROSS-SECTIONS 3. p AND anti-p INDUCED REACTIONSBy High-Energy Reactions Analysis Group (V. Flaminio et al.). CERN-HERA-79-03, Oct 1979. 254 pp.
50 b
total (pp ) ' 70 mb
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Shape of BackgroundDual Parton Model (DPM)
Kinematic situation favourable→ background decreases just below J/ mass
Capella, Sukhatme, Tan, Tran Thanh VanPhys. Rept. 236(1994)225Kaidalov, Volkovitsky, Z. Phys. C63(1994)517Uzhinsky, Galoyanhep-ph/0212369
Shape varyingacross J/ signal regionFit by 1st order Chebyshev polynom
2 days data taking
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Scan of a Resonance R
Convolution of resonance width and beam resolution
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MC, X(3872) Scan, each 2 days, p/p = 10-5 mode
6990.84 MeV
6990.96 MeV
6990.88 MeV 6990.92 MeV
6991.00 MeV
6991.08 MeV 6991.12 MeV 6991.16 MeV
6991.04 MeV
Tagged J/ yield, 2-particle invariant mass / GeV
Mass(e+e−) / GeV
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X(3872) Excitation Function, MC
Exclusive final state
pp → X(3872)
each data point 2 daysdata taking
full background Preliminary result:
fitted width is ~20% larger than input,but (s) still ·100 keV(this would be a syst. erroron the width of X(3872))
Unfolding (integral equation)is ongoing work(Master Thesis, Univ. Gießen)
Preliminary estimate for Panda¸168 keV for p/p=10−4
s / GeVX
(3872)
yie
ld
Reconstruction efficiency '72%
Preliminarystat. errors only
3.8718 3.8720 3.8722
'79 keV
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Summary
For the 1st time, MC simulations for X(3872) production at Panda have been performed
Detailed simulation and reconstruction: final state radiation vector → vector angular distribution track finder and track fitter PID by track and cluster matching background with dual parton model
Preliminary results are encouraging Extraction of width is ongoing
(integral equation)
For more information about FAIR see Talkby Ulrich Wiedner, Plenary, Friday
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Details of MC Scan Signal X(3872)
Geant3.21 PHOTOS on,angular distribution V ! V PS PS
Background DPM with fast simulation(detector resolution parametrized)
input beam resolution not varyingover scan range
Track finder and track fitterusing TPC and MVDNHits and 2 Cut
Background assumednot varying with s
statistical errors only in fit yield outside is assumed zero
(but hadronic cross section is high)
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Resonance Scan
Note: the cross section depends on the spin J of the resonance! a way to determine the quantum number of X(3872)
R isindependant from BR x BRbecause it onlyenters into peak
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28Sören Lange | X(3872) at Panda
The Pellet Target
Here: WASA Targetd=25 mfall speed ¸ 60 m/s
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29Sören Lange | X(3872) at Panda
MVD (Micro Vertex Detector)
4 barrels & 8 disks inner layers pixels outer layers strips forward mixed
Silicon Pixel Detectors 120 modules 100x100 µm2 pixel size ~107 readout channels maximum rate
<10 MHits s–1 per module Radiation length
~1% X0 per layer Silicon Strip Detectors
400 modules ~0.5 m2 active area 7x104 readout channels
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 p/GeV/c
dE/d
x (
a.u
.) K pe
MVDdE/dx
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30Sören Lange | X(3872) at Panda
STT (Straw Tube Tracker) ~4100 tubes, axial or skewed
(15 double layers) R=15.5-41.5 cm L=1.5m (only) m=50 kg tube diameter 10mm
wall Mylar, 30μm anode wire W/Re, 20μm spatial resolution
σrφ≈150μm (axial layers)σz≈3-10mm (skewed layers)
gas 90%Ar,10%CO2
over-pressurefor stabilization p=2 bar
radiation length ~1-1.3% X0
wire U=2 kV pT/pT ' 1.2% prototype under investigation
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TPC (Time Projection Chamber) R=15.5-41.5 cm 135 padrows 135,169 pads of 2x2 mm2
Multi-GEM for amplification and ion backflow suppression
Gas: Ne/CO2 (+CH4/CF4) 50-70 µs drift time
! 700 events pile-up gating grid continously open p/p'1% prototype
under investigation
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DIRC(Detection of Internally Reflected Cerenkov Light)
16 Quartz (n=1.47) Bars
d=1.7 cm, R=48 cmBaBar design
electron0.7 GeV/c
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EMC (Electromagnetic Calorimeter)~17,200 crystalsPbWO4 (radiation hard, fast Decay~6 ns)28 X0
dE/dx=13.0 MeV/cm
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EMC (Electromagnetic Calorimeter) operated at T=–25o C
E/p
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MUO (Muon Detector) R = 1.3–1.8 m tubes (for x coordinate)
gold plated tungsten wire, d=0.05 mm, L=4 m, wire U=+3.6 kV, cathode U=-1.2 kV
copper strips (for z coordinate)U=+1.8 kV
! pad size 1x1 cm2
view from GeoManager
x
y
z
d=1 cm
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36Sören Lange | X(3872) at Panda
Resonance Scan
Note: the cross section depends on the spin J of the resonance! a way to determine the quantum number of X(3872)
R isindependant from BR x BRbecause it onlyenters into peak
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37Sören Lange | X(3872) at Panda
Chen and Ma Estimate
Prediction for cross section with X as loosely bound DD* state Chen, Ma, Phys. Rev. D77(2008)097501
width X 136 keV - 2.3 MeVcross section 3.57 - 443nb
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39Sören Lange | X(3872) at Panda
Charmonium Production Cross Section in ppbar
Barnes, Li,Phys.Rev.D75:054018,2007.hep-ph/0611340
5 nbWith one additional meson
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40Sören Lange | X(3872) at Panda
Dual Parton ModelA. Capella, U. Sukhatme, C.-I. Tan, andJ. Tran Thanh Van, Phys. Rept. 236, 225(1994). A. B. Kaidalov and P. E. Volkovitsky, Z.Phys. C63, 517 (1994).[12] V. V. Uzhinsky and A. S. Galoyan,hep-ph/0212369 (2002).
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(2S)! J/ + − as reference channel
§ from X(3872) have higher momentumReconstruction efficiency is ' 21% higher
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Variation of Angular Distributions With PID Cut PHOTOS ON (in X decay and J/Psi decay),
e+e− only (no Muons) Negigible effect on reconstruction efficiency (< 1%)
! Lorentz boost is dominating angular distribution
Phasespace V ! V PS PS
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43Sören Lange | X(3872) at Panda
Comparison of e+ e− and + − final states
Radiative Tail in J/ mass generates tail at higher masses in 4-particle invariant mass
' 5 daysdata taking
4-particle invariant mass