Transcript L3 Trigger

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 Gießen
for the PANDA Collaboration
12th International Conference
on Meson-Nucleon Physics and the Structure of the Nucleon
05/31-06/04, 2010
College of William and Mary
Williamsburg, Virginia
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
The X(3872)
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A charmonium(-like) state found in
X(3872) → J/ + −
Observation
of decay into J/ 
→ C=+1
interesting properties:
breaks isospin in the decays
J/(! + −), J/(! + − 0)
→ is it charmonium?
Within  m < 1 MeV
of the DD* threshold
S-wave molecular state?
(to be) investigated at
Belle, BaBar, CDF-II, D0
BES-III, Belle-II
However:
width is unknown
<2.3 MeV (Belle)
Sören Lange | X(3872) at Panda
Belle
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Charmonium Production inpp collisions
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X(3872) has C=+
In e+e− collisions only JPC=1–− can be produced directly
inpp collisions any quantum number
2 gluons: 0−+, 0++, 2++
J=0,2
3 gluons: 1−−, 1+−
J=1
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Resonance scan with a cooled anti-proton beam:
the width of the X(3872) could be measured
! Panda Experiment at FAIR
Sören Lange | X(3872) at Panda
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GSI today
Future facility
2R=1.084 km
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HESR (High Energy Storage Ring)
For Anti-Protons
High intensity mode
• 1011 p
PANDA
• p/p  104 (stochastic cooling)
High resolution mode
• 1010 p
5
• p/p  10 (e– cooling)
' 2 x 109
J/ per year
Sören Lange | X(3872) at Panda
Internal targets
• L  21032 cm -2s -1
• Pellets
• Cluster jet
• Nuclei: Be, C, Si, Al
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The Pellet Target
Here: WASA Target
d=25 m
fall speed ¸ 60 m/s
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beam momentum resolution
p/p‚ 2 £ 10−4
→ s FWHM resolution 0.5 MeV
 £ BR (J/) ' 630 nb
Sören Lange | X(3872) at Panda
Events/Luminosity (nb)
 (J/) = 99 § 12 § 6 keV
 (´) = 306 § 36 § 16 keV
by FERMILAB E760 and E835
Events/Luminosity (nb)
Example of Charmonium Width Measurements
Phys. Rev. D 47(1993)772
30
25
J/
20
15
10
5
5
4
´
3
2
1
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Panda Experiment
MVD Micro Vertex Detector
TPC Time Projection Chamber
EMC Electromagnetic Calorimeter
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PandaRoot Framework
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Simulation,
Digitization
Reconstruction,
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 Book
arXiv: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 information
http://panda-wiki.gsi.de/cgi-bin/view/Computing/PandaRoot
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PandaRoot Implementation of relevant Detectors
TPC
MVD
135 padrows
135,169 pads of 2x2 mm2
120 pixel modules
100x100 µm2 pixel s
~107 readout chann
EMC
~17,200 crystals
PbWO4 (radiation hard, fast decay~6 ns)
28 X0
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400 strip modules
~0.5 m2 active area
7x104 readout chann
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Estimated Rates for X(3872) Formation at Panda
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pbeam=6.99100 GeV/c
Baseline assumption: peak = 50 nb
If X is a loosely bound DD* state
Chen, Ma, Phys. Rev. D77(2008)097501
cross 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
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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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X(3872)! J/ + – Event, PandaRoot Simulation
Targetpipe
Beampipe
e§
Beampipe
§
e§
§
Targetpipe
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X(3872) Events in Panda MVD+TPC
PandaRoot Simulation
XYZ coordinates / cm
XYZ coordinates / cm
Beampipe
Interaction
XYZ coordinates / cm
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Comparison of e+ e− and + − final states
2-particle invariant mass
Combinatorial
Background
only
Radiative Tail due to
Final 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
without
PID
J/
4-particle invariant mass
X(3872)
with
PID
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Variation of Angular Distributions
Panda is fixed target experiment
 Negligible effect on reconstruction efficiency (<1%)
 ! Lorentz boost dominates acceptance
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phasespace
Sören Lange | X(3872) at Panda
vector → vector
+ pseudoscalar
+ pseudoscalar
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Kinematic Fit: Vertex Constraint and Mass Constraint
Example:
reference mode
´ ! J/ + –
J/
No fit
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No fit
‘
Fit
Constraint
J/
Fit
m'3 MeV
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Background: pp ! 2 + 2 −
total (pp ) ' 70 mb
COMPILATION OF CROSS-SECTIONS
3. p AND anti-p INDUCED REACTIONS
By High-Energy Reactions Analysis Group
(V. Flaminio et al.).
CERN-HERA-79-03, Oct 1979. 254 pp.
50 b
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Shape of Background
Dual Parton Model (DPM)
Capella, Sukhatme, Tan, Tran Thanh Van
Phys. Rept. 236(1994)225
Kaidalov, Volkovitsky,
Z. Phys. C63(1994)517
Uzhinsky, Galoyan
hep-ph/0212369
Kinematic situation favourable
→ background decreases just below J/ mass
2 days data taking
Shape varying
across J/ signal region
Fit by 1st order
Chebyshev polynom
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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
Tagged J/ yield, 2-particle invariant mass / GeV
6990.84 MeV
6990.88 MeV
6990.92 MeV
6990.96 MeV
6991.00 MeV
6991.04 MeV
6991.08 MeV
6991.12 MeV
6991.16 MeV
Mass(e+e−) / GeV
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X(3872) Excitation Function, MC
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Exclusive final state
pp → X(3872)
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each data point
2 days
data taking
full background
Preliminary result:
fitted width is ~20% larger
than input,
but (s) still ·100 keV
(this would be a syst. error
on 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
Sören Lange | X(3872) at Panda
X(3872) yield
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Reconstruction
efficiency '72%
'79 keV
3.8718
3.8720
3.8722
s / GeV
Preliminary
stat. errors only
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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)
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 For more information about FAIR see Talk
by Ulrich Wiedner, Plenary, Friday
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Backup
Details of MC Scan
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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 varying
over scan range
Track finder and track fitter
using TPC and MVD
NHits and 2 Cut
Background assumed
not 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
R is
independant
from BR x BR
because it only
enters into peak
Note: the cross section depends on the spin J of the resonance
! a way to determine the quantum number of X(3872)
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The Pellet Target
Here: WASA Target
d=25 m
fall speed ¸ 60 m/s
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MVD (Micro Vertex Detector)
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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
MVD
dE/dx
dE/dx (a.u.)
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
e
0
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0.1
K
0.2
0.3
0.4
p
0.5
0.6
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0.7 0.8
p/GeV/c
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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-pressure
for 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)
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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
cm
BaBar design
electron
0.7 GeV/c
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EMC (Electromagnetic Calorimeter)
~17,200 crystals
PbWO4 (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)
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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
Sören Lange | X(3872) at Panda
view from
GeoManager
y
z
x
d=1 cm
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Resonance Scan
R is
independant
from BR x BR
because it only
enters into peak
Note: the cross section depends on the spin J of the resonance
! a way to determine the quantum number of X(3872)
Sören Lange | X(3872) at Panda
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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 MeV
cross section 3.57 - 443nb
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1+ vs. 1-
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Charmonium Production Cross Section in ppbar
Barnes, Li,
Phys.Rev.D75:054018,2007.
hep-ph/0611340
With one
additional
meson
5 nb
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Dual Parton Model
A. Capella, U. Sukhatme, C.-I. Tan, and
J. 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 momentum
Reconstruction 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
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Phasespace
Sören Lange | X(3872) at Panda
V ! V PS PS
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Comparison of e+ e− and + − final states
4-particle invariant mass
Radiative Tail in J/ mass generates tail
at higher masses in 4-particle invariant mass
' 5 days
data taking
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Resonance Scan
Double scan
technique
Constant
Orbit
Constant
Field
(beam energy
is changed by
stochastic
cooling
pick-ups)
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