Transcript Charmonium at PANDA - Istituto Nazionale di Fisica Nucleare

CHARMONIUM AT
Agnes Lundborg
QWG workshop
Brookhaven June 2006
Agnes Lundborg
Uppsala University
Sweden
CHARMONIUM AT
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.
Charmonium spectrum
potential models vs.data
dashed: nonrel (left), Godfrey-Isgur (right)
• PANDA as next generation (2011)
• What, why and how can PANDA
do better?
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Proton-antiproton versus
electron-positron
1   in  cc 
--
e e  ψ   cc  + X
+ -
Formation
The two particles fuse into
the intermediate state.
pp   cc 
Agnes Lundborg
QWG workshop
Brookhaven June 2006
Production
The state is reached through decays
or nonresonant production.
CHARMONIUM AT
Typical resolution in
production
Proton-antiproton E835
Energy spread in beam
s  0.4 MeV
PDG Γ χ c1  0.91 MeV
Agnes Lundborg
QWG workshop
Brookhaven June 2006
100
CBall
E835
cc1
1000
E 835 ev./pb
Typical resolution in
formation
E835, Ambrogiani et al., PRD 62 (2000) 052002
CBall ev./2 MeV
Crystall Ball e+e- cc1 Γ < 8 MeV
Resolution of nonvector charmonium
depends on the detector.
B-factories and other current
e+e- experiments (BES, CLEO-c)
CBall, Edwards et al. PRL 48 (1982) 70
3500
3510
CHARMONIUM AT
3520 MeV
ECM
Scanning mode
Discovery in production and precision measurement in scanning.
Resonance shape
(Breit Wigner?)
Measured cross section
Beam momentum
profile
ECM
Important for: cross section shape measurements
Precision measurements on mass and widths both at
resonance-energies and two-meson thresholds.
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
HESR at FAIR
High Energy Storage Ring
Storage ring for p
Np = 5×1010 pbeam = 1.5 -15 GeV c
High density target
pellet 1015 atoms/cm2 ,cluster jet, wire
High luminosity mode
stochastic cooling
Δp
p
 10-4 L = 2×1032 cm-2s-1
High precision mode
Electron cooling to 8 GeV
Δp
p
 10-5 L  1031 cm-2s-1
Agnes Lundborg
QWG workshop
Brookhaven June 2006
Δp
p
 10-5 gives Δp = 50 keVat p = 5 GeV!!!
CHARMONIUM AT
QCD conceptually allows for states where
gluons contribute to the quantum numbers
Calculation flux-tubemodel, latticeQCD, bag-model, constituent
gluonmodel.
Spin - exotichybrids 1-+ ,0+- , 2+-
Meson qq
Observations in the light quark sector:
•Exotic qn. 1-+
Hybrid?
π1 (1400) E852(πp) Crystal Barrel(pp)
π1 (1600) E852(πp) Crystal Barrel(pp)
•Difficult to identify in the light quark sector, many overlapping
states which mix.
Glueball gg
Hybrid qqg
Agnes Lundborg
QWG workshop
Brookhaven June 2006
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!
CHARMONIUM AT
A possible exotic charmonium hybrid channel:
pp
 g / 
c c1 ( )s
Nonrelativistic decay:
charmquarks stay as they
are. Gluonic excitation goes
into a light scalar.
Lowest energy charmonium hybrid
(spin-exotic)
J PC  1
M  4.1  4.4 GeV
  (20) MeV
[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)]
Agnes Lundborg
QWG workshop
Brookhaven June 2006
Production mode JPC=1-+
J 
Final state:
7 photons! 1 lepton pair!
We need:
1 Excellent calorimeter
with full angular range
coverage.
ee  
 


Good experimental
tag!
CHARMONIUM AT
We need an excellent:
Electromagnetic Calorimeter (EMC)
Almost 4π -acceptance
barrel plus endcaps
Compact material (PWO, BGO)
Granularity (Molière radius)
Low threshold tens of MeV
p
Readout inside magnetic field: APD
Also high energy photons GeV
22 radiation lengths of crystal
Timing 1 ns – triggering
And high count rate (10 annihilations per s)
7
Radiation hardness (less radiation than CMS)
Last thing to solve: High resolution requires a large light output!
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Cooperation with manufacturers
in Bogoroditsk and Shanghai
working with doping and crystal growth
processes has produced better crystals.
Third generation PWO
with much larger light yields and therefore
better resolution.
But that is not enough!
Cooling
-25°C gives overall good performance.
Already at acceptable resolutions!
Panda
becomes
a Polarbear
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Charmonium production
pp  cc  m m   0 ,,,  0 , ,   ...
Complicated QCD process!
Only theoretical guideline PCAC
for only one channel.
p
J
p
0
 ( pp  J  0 )  100 pb
at 3.5 GeV off  resonance
[Claudia Patrigniani E 835]
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Use experimental data
we extrapolate to…
we know…


cc p pp  m known amplitude
A

extrapolate A to pp  cc  m


J/
?
A
[A.Lundborg, T.Barnes, U. Wiedner
PRD73 (2006) 096003.]
A
p
It’s a kinematical extrapolation,
notpvery far..
J/
p
weWe
extrapolate
to… decay width…
know this
Example: what is the cross section for

pp J/ ?


p
know… not widely separated kinematically:
we extrapolate to…
These processes areweactually
A


Width proportional to
Dalitz area


p
Integrate
p
J/
J/
A
We want to know this cross
section.
Agnes Lundborg
ated
kinematically:
A
p
p
p
CHARMONIUM
QWG workshop
These processes are actually not widely
separated kinematically:
Brookhaven June 2006
J/
AT
Results
Isoscalar  ,  '
enhanced ?
Constant amplitude?
First estimates.
Cross section in the order between
10 pb to 1 nb
200 to 20 000 events per day.
Background 10 000 000 events
per second.
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Technical Progress Report
simulations
All neutral channel
pp  ηπ0 π0  6γ
No significant structures or regions of
poor efficiency for the calorimeter
setup.
Charmed hybrid – red curve
pp  g, g  cc ( 0 0 )swave , cc  J  
•7 photons, 2 oppositely charged tracks
•Mass window cuts on the intermediate particles.
Gives 12% detection efficiency.
Any possible background would includes a
J  and many photons.
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
pp  c  
Measured at E835 about 50 pb
in the region | cosθ |< 0.25
Event selection
•Exactly two neutral tracks.
•No charged tracks.
•No pion candidates
| mγγ - mπ0 |< 25 MeV
•Invariant mass energy window
| Eγγ - Epp |CM < 0.4 GeV
•Momentum of candidate <0.4 GeV/c
o
•Opening angle >178.5
•Momentum angle
| cosθ |< 0.25
[E835, PLB 566 (2003) 45-50]
ηc efficiency 10.3%
Major background sources
pp  π0 π0
pp  π0 γ
#Signal
= 5.1
#Background
Signal
Background
[E835, PRD 56, 5 (1997) 2509(23)]
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
PANDA Identification and tracking of:
Cherenkovs and TOF
MVD
EMC
D , D , K , K , π , π , μ , e ,γ
±
0
±
p,p, Λ, Σ, Ξ
Agnes Lundborg
QWG workshop
Brookhaven June 2006
0
±
Trackers and
B-fields
0
±
±
Muon chamber
CHARMONIUM AT
Micro vertex detector
Displaced vertices of open charm and strangeness
±
D± , D0 , Ds cτ order of 100μm
K s0 , Λ, Σ cτ order of 1 - 10 cm
Build on ALICE, ATLAS and CMS
experience with hybrid detectors.
Silicon pixel (3 layers) and strips
(2 layers)
7.2 million barrel pixels, 2 million
forward pixels
14cm
R&D:
Requirements on pixel size and
orientation.
Investigate photon conversions
(cooling system, electronics,
detector).
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Central tracking – two alternatives
2 T axial B-field, same space, forward direction MWPCs.
Time projection chamber
+Low material budget.
+dEdx particle ID.
High rates 107 events per second
->Ungated TPC
-Space charge from ions
-Overlaying events requires very good
resolution for disentangling
+GEM-foils (Gas electron multiplier)
Straw tube tracker
10000 straws
Z-coordinate from either:
-Skew angle 7-15 mm
-Charge sharing 3 mm
-Maximum material 3% X/X0
+Handles rates and has no space charge
problem
10000 holes/cm2
74 cm
TPC prototype in Munich
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
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 and
civil construction on-going.
Beam-on in: (Maybe) 2011
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
PANDA 2006: 300 people, 15 countries, 46 institutes
Technical Progress Report in february 2005
timelines, plans, simulations, technical solutions and R&D-work.
[PANDA technical progress report
http://www-panda.gsi.de]
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT
Accessible physics
Agnes Lundborg
QWG workshop
Brookhaven June 2006
CHARMONIUM AT