Prospects for X(3872) Detection at Panda Jens Sören Lange, Martin Galuska, Thomas Geßler, Wolfgang...

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

MENU10, Williamsburg, June 2, 2010

2Sören Lange | X(3872) at Panda

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



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



GSI todayGSI todayFuture facilityFuture facility

2R=1.084 km



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



The Pellet Target

Here: WASA Targetd=25 mfall speed ¸ 60 m/s



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



Panda Experiment

MVD Micro Vertex DetectorTPC Time Projection ChamberEMC Electromagnetic Calorimeter



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



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



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



X(3872)! J/ + – Event, PandaRoot Simulation

Beampipe

Beampipe

Targetpipe

Targetpipe

e§

e§

§

§



X(3872) Events in Panda MVD+TPC PandaRoot Simulation

BeampipeInteraction

XYZ coordinates / cm XYZ coordinates / cm

XYZ coordinates / cm



Comparison of e+ e− and + − final states

CombinatorialBackgroundonly

2-particle invariant mass

Radiative Tail due toFinal state radiation(PHOTOS)



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



Example MC Results for X(3872)! J/ + −

2-particle invariant mass 4-particle invariant mass

X(3872)J/

withoutPID

withPID



Variation of Angular Distributions

Panda is fixed target experiment Negligible effect on reconstruction efficiency (<1%) ! Lorentz boost dominates acceptance

phasespacevector → vector+ pseudoscalar+ pseudoscalar



Kinematic Fit: Vertex Constraint and Mass Constraint

Example:

reference mode

´ ! J/ + –

No fit No fit

Fit Fit

J/ ‘

J/ ‘

Constraint

m'3 MeV



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



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



Scan of a Resonance R

Convolution of resonance width and beam resolution



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



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



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

Backup



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)



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



The Pellet Target

Here: WASA Targetd=25 mfall speed ¸ 60 m/s



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



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



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



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



EMC (Electromagnetic Calorimeter)~17,200 crystalsPbWO4 (radiation hard, fast Decay~6 ns)28 X0

dE/dx=13.0 MeV/cm



EMC (Electromagnetic Calorimeter) operated at T=–25o C

E/p



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



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



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



1+ vs. 1-



Charmonium Production Cross Section in ppbar

Barnes, Li,Phys.Rev.D75:054018,2007.hep-ph/0611340

5 nbWith one additional meson



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).



(2S)! J/ + − as reference channel

§ from X(3872) have higher momentumReconstruction efficiency is ' 21% higher



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



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



Resonance Scan

Double scantechnique

Constant Orbit

Constant Field(beam energy is changed bystochasticcooling pick-ups)

Prospects for X(3872) Detection at Panda Jens Sören Lange, Martin Galuska, Thomas Geßler, Wolfgang...

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