agnes lundborg uppsala university sweden charmonium at · cball ev./2 mev 100 e cm cball 1000 e 835...
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CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Jost Lühning
CHARMONIUM AT
Agnes LundborgUppsala University
Sweden
Background
• We thought that we understood charmonium quite well. Positronium of QCD, medium heavy quarks, potential model, narrow states. Perfect laboratory!
• In the last few years the B-factories and CLEO-c have been making unexpected discoveries. BESIII is coming up. E835 and Crystal Barrel are done.
• PANDA as next generation (2011)• What, why and how can PANDA
do better?
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
M [GeV]
S P
ψ(3770)
D
ψ(4159)
ψ’(3686)
ψ(3097)
ηc(2979)
χ2(3556)
χ0(3415)
χ1(3511)
η’c(3638)
J/
0+
0-
2+
1+
1-
ψ(4040)
ψ(4415)
F G
1-
1-
1-
0-
1-
1-
DD
Charmonium spectrumpotential models vs.datadashed: nonrel (left), Godfrey-Isgur (right)
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
( )--1 in ccψ=
( )
( )
→ →
→
+ -e e ψ cc + X
pp cc
FormationThe two particles fuse intothe intermediate state.
Proton-antiproton versus electron-positron
ProductionThe state is reached through decaysor nonresonant production.
3500 3520 MeV3510
CBal
l ev
./2 M
eV
100
ECM
CBall
1000
E 8
35 e
v./p
b
χc1E835
CBall, Edwards et al. PRL 48 (1982) 70
E835, Ambrogiani et al., PRD 62 (2000) 052002
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Typical resolution in productionCrystall Ball e+e-Resolution of nonvector charmoniumdepends on the detector.B-factories and other currente+e- experiments (BES, CLEO-c)
Typical resolution information
Proton-antiproton E835Energy spread in beam
1cχ Γ < 8MeV
≈≈
c1χ
s 0.4MeVPDG Γ 0.91MeV
ECM
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Discovery in production and precision measurement in scanning.
Important for: cross section shape measurementsPrecision measurements on mass and widths both at
resonance-energies and two-meson thresholds.
Resonance shape(Breit Wigner?)
Beam momentumprofile
Measured cross section
Scanning mode
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Storage ring for p
High density targetpellet ,cluster jet, wire
High luminosity modestochastic cooling
High precision modeElectron cooling to 8 GeV
10pN = 5×10 beamp = 1.5 -15 GeV c
≈ -4 32 -2 -1Δp 10 L = 2×10 cm sp
5 1≈ ≈- 3 -2 -1Δp 10 L 10 cm sp
15 210 atoms/cm
HESR at FAIRHigh Energy Storage Ring
5 5 5≈ -Δp 10 gives Δp = 0 keVatp = GeV!!!p
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Glueball gg
Calculation flux-tubemodel, latticeQCD, bag-model, constituentgluonmodel.
Observations in the light quark sector:
•Exotic qn. 1-+Hybrid?
•Difficult to identify in the light quark sector, many overlapping states which mix.
Charmonium energy region•Light quark form a structureless continuum with few heavier states on top.
•A spin exotic can be seen in production but not formation and would then immediately be identified as interesting.Model independently! Without a complicated formalism!
QCD conceptually allows for states wheregluons contribute to the quantum numbers
Hybrid qqg
Meson qq
1
1
π (1400) E852(πp) Crystal Barrel(pp)π (1600) E852(πp) Crystal Barrel(pp)
-+ +- +-Spin - exotichybrids 1 ,0 ,2
Nonrelativistic decay:charmquarks stay as they are. Gluonic excitation goes into a light scalar.
Production mode JPC=1-+p p /gψ π η
1( )c sχ ππ
J ψ γ
e e μ μ+ − + −
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Lowest energy charmonium hybrid
(spin-exotic)
[C.Bernard, Phys.Rev. D56 (1997) 7039][F.E. Close, Phys. Rev. 1998][P.R. Page, Acta Phys. Polon. 1998][P. Page, Phys Lett.B402(1997)][UKQCD, McNeile, Phys. Rev. D56(2002)]
1 4.1 4.4(20)
PCJ M GeVMeV
−+= = −Γ = Ο
Good experimentaltag!
Final state:7 photons! 1 lepton pair!We need:1 Excellent calorimeterwith full angular range coverage.
A possible exotic charmonium hybrid channel:
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
We need an excellent:Electromagnetic Calorimeter (EMC)
Almost -acceptance barrel plus endcaps
Compact material (PWO, BGO)
Granularity (Molière radius)
Low threshold tens of MeVReadout inside magnetic field: APD
Also high energy photons GeV22 radiation lengths of crystal
Timing 1 ns – triggeringAnd high count rate (10 annihilations per s)
Radiation hardness (less radiation than CMS)
Last thing to solve: High resolution requires a large light output!
4π
7
p
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Cooperation with manufacturersin Bogoroditsk and Shanghaiworking with doping and crystal growthprocesses has produced better crystals.
Third generation PWOwith much larger light yields and thereforebetter resolution.
But that is not enough!Cooling
gives overall good performance.Already at acceptable resolutions!-25°C
Panda becomes
a Polarbear
0
[ 835]
( ) 1003.5
Claudia Patrigniani E
pp J pbat GeV off resonanceσ ψπ→ ≅
−
0 0, , , , , ...pp cc m m π η ω ρ φ π π+ −→ + =Complicated QCD process!Only theoretical guideline PCACfor only one channel.
0πJ ψp
p
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Charmonium production
Use experimental data
cc pp m known amplitude Aextrapolate A to pp cc m
→ +→ +
We know this decay width…
It’s a kinematical extrapolation, not very far..
π0
J/ψ
p
p
A
[A.Lundborg, T.Barnes, U. WiednerPRD73 (2006) 096003.]
Integrate
Width proportional toDalitz area
J/ψ
π0
p
p
A
We want to know this crosssection.
π0
J/ψ
p
p
A
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Constant amplitude?First estimates.Cross section in the order between10 pb to 1 nb200 to 20 000 events per day.Background 10 000 000 events per second.
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Results, '
?Isoscalarenhanced
η η
Technical Progress Report simulations
All neutral channel
No significant structures or regions of poor efficiency for the calorimetersetup.
→ →0 0pp ηπ π 6γ
Charmed hybrid – red curve
•7 photons, 2 oppositely charged tracks•Mass window cuts on the intermediate particles.
Gives 12% detection efficiency.Any possible background would includes a
and many photons.
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
J ψ
0 0, ( ) ,g g c s wave c Jψ η ψ χ π π χ ψ γ−→ → →pp
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Signal
Background
[E835, PLB 566 (2003) 45-50]
cpp η γγ→ →Measured at E835 about 50 pbin the region | cosθ |< 0.25
Major background sources→ 0 0pp π π → 0pp π γ
[E835, PRD 56, 5 (1997) 2509(23)]
Event selection•Exactly two neutral tracks.•No charged tracks.•No pion candidates
•Invariant mass energy window
•Momentum of candidate <0.4 GeV/c•Opening angle >178.5•Momentum angle
0γγ π|m -m |< 25MeV
γγ pp CM| E -E | < 0.4 GeV
o
| cosθ |< 0.25
cη efficiency 10.3%#Signal = 5.1
#Background
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
± 0 ± 0 ± 0 ± ±D , D , K , K , π , π , μ , e , γp,p, Λ, Σ,Ξ
PANDA Identification and tracking of:
MVDCherenkovs and TOF
Muon chamberTrackers andB-fields
EMC
Micro vertex detector
Displaced vertices of open charm and strangeness
Build on ALICE, ATLAS and CMS experience with hybrid detectors.Silicon pixel (3 layers) and strips (2 layers)7.2 million barrel pixels, 2 millionforward pixels
R&D:Requirements on pixel size and orientation.Investigate photon conversions(cooling system, electronics, detector).
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
±± 0s
0s
D ,D ,D cτ order of 100μm
K , Λ, Σ cτ order of 1-10 cm
14cm
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
Time projection chamber+Low material budget. +dEdx particle ID.High rates events per second->Ungated TPC-Space charge from ions-Overlaying events requires very goodresolution for disentangling+GEM-foils (Gas electron multiplier)
Central tracking – two alternatives2 T axial B-field, same space, forward direction MWPCs.
Straw tube tracker10000 strawsZ-coordinate from either:-Skew angle 7-15 mm -Charge sharing 3 mm-Maximum material+Handles rates and has no space chargeproblem
710
210000 holes/cm
03%X/X
74 cm
TPC prototype in Munich
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
To conclude:
Panda will provide the next generation of charmonium knowledge!Precision – state of the art detectors, formation versus production.Rates – pellet target, beam. Proton-antiproton.Scope - detection of charged and neutral particles over (almost) full phase space
Charmonium energy region•Charmonium•Charmonium hybrids•Glueballs•DD-thresholds•Meson molecules•Other topics: hypernuclei, drell-Yan,charm in nuclei, di-baryons, crossed channel compton scattering.
Hardware R&D, software optimization andcivil construction on-going.Beam-on in: (Maybe) 2011
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
PANDA 2006: 300 people, 15 countries, 46 institutesTechnical Progress Report in february 2005 timelines, plans, simulations, technical solutions and R&D-work.
[PANDA technical progress reporthttp://www-panda.gsi.de]
CHARMONIUM ATAgnes LundborgQWG workshopBrookhaven June 2006
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