Transcript Diapositiva 1

Physics with the PANDA
Detector at GSI
Diego Bettoni
Istituto Nazionale di Fisica Nucleare, Ferrara
First Meeting of the APS Topical Group on Hadronic Physics
Fermilab, 25 October 2004
Outline
• Overview of the Project
• PANDA Physics Program
– Charmonium Spectroscopy
– Hybrids and Glueballs
– Hadrons in Nuclear Matter
• The PANDA Detector Concept
• Timeline
• Conclusions
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The GSI FAIR Facility
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FAIR: Facility for Antiproton and Ion Research
Primary Beams
•1012/s; 1.5 GeV/u; 238U28+
•Factor 100-1000 over present in intensity
•2(4)x1013/s 30 GeV protons
•1010/s 238U73+ up to 25 (- 35) GeV/u
Secondary Beams
•Broad range of radioactive beams up to
1.5 - 2 GeV/u; up to factor 10 000 in
intensity over present
•Antiprotons 3 - 30 GeV
Storage and Cooler Rings
Key Technical Features
•Cooled beams
•Rapidly cycling superconducting magnets
•Radioactive beams
•e – A collider
•1011 stored and cooled 0.8 - 14.5
GeV antiprotons
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Antiproton Physics Program
• Charmonium Spectroscopy. Precision measurement of masses,
widths and branching ratios of all (cc) states (hydrogen atom of
QCD).
• Search for gluonic excitations (hybrids, glueballs) in the charmonium
mass range (3-5 GeV/c2).
• Search for modifications of meson properties in the nuclear medium,
and their possible relation to the partial restoration of chiral symmetry
for light quarks.
Topics not covered in this presentation:
• Precision -ray spectroscopy of single and double hypernuclei, to
extract information on their structure and on the hyperon-nucleon and
hyperon-hyperon interaction.
• Electromagnetic processes (DVCS, D-Y, FF ...) , open charm physics
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The GSI p Facility
HESR = High Energy Storage Ring
• Production rate 2x107/sec
• Pbeam = 1 - 15 GeV/c
• Nstored = 5x1010 p
High luminosity mode
• Luminosity
= 2x1032 cm-2s-1
• p/p~10-4 (stochastic cooling)
High resolution mode
• p/p~10-5 (el. cooling < 8 GeV/c)
• Luminosity
= 1031 cm-2s-1
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The PANDA Collaboration
More than 300 physicists from 48 institutions in 15 countries
U Basel
IHEP Beijing
U Bochum
U Bonn
U & INFN Brescia
U & INFN Catania
U Cracow
GSI Darmstadt
TU Dresden
JINR Dubna
(LIT,LPP,VBLHE)
U Edinburgh
U Erlangen
NWU Evanston
U & INFN Ferrara
U Frankfurt
LNF-INFN Frascati
U & INFN Genova
U Glasgow
U Gießen
KVI Groningen
U Helsinki
IKP Jülich I + II
U Katowice
IMP Lanzhou
U Mainz
U & Politecnico & INFN
Milano
U Minsk
TU München
U Münster
BINP Novosibirsk
LAL Orsay
U Pavia
IHEP Protvino
PNPI Gatchina
U of Silesia
U Stockholm
KTH Stockholm
U & INFN Torino
Politechnico di Torino
U Oriente, Torino
U & INFN Trieste
U Tübingen
U & TSL Uppsala
U Valencia
IMEP Vienna
SINS Warsaw
U Warsaw
Spokesman: Ulrich Wiedner (Uppsala)
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QCD Systems to be studied in Panda
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Charmonium Spectroscopy
Charmonium is a powerful tool for the
understanding of the strong interaction.
The high mass of the c quark (mc ~ 1.5
GeV/c2) makes it plausible to attempt a
description of the dynamical properties of
the (cc) system in terms of non relativistic
potential models, in which the functional
form of the potential is chosen to reproduce
the known asymptotic properties of the
strong interaction. The free parameters in
these models are determined from a
comparison with experimental data.
2  0.2 s  0.3
Non-relativistic potential models +
Relativistic corrections + PQCD
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Experimental Study of Charmonium
pp annihilation
e+e- annihilation
•
Direct formation only possible for
JPC = 1-- states.
• All other states must be produced
via radiative decays of the vector
states, or via two-photon
processes, ISR, B-decay, double
charmonium.
Good mass and width resolution for
the vector states. For the other states
modest resolutions (detector-limited).
•
•
Direct formation possible for all
quantum numbers.
Excellent measurement of masses
and widths for all states, given by
beam energy resolution and not
detector-limited.
In general, the measurement of
sub-MeV widths not possible in e+e-.
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Experimental Method in pp Annihilation
The cross section for the process:
pp cc  final state
is given by the Breit-Wigner formula:
 BW
Bin Bout R2
2J 1 

4 k 2  E  M R 2  R2 / 4
The production rate  is a convolution of the
BW cross section and the beam energy distribution function f(E,E):
  L0   dEf ( E , E ) BW ( E )   b 
The resonance mass MR, total width R and product of branching ratios
into the initial and final state BinBout can be extracted by measuring the
formation rate for that resonance as a function of the cm energy E.
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Hot Topics in Charmonium Spectroscopy - I
•
Discovery of the c(21S0) by Belle
(+BaBar, CLEO).
c
c
M(c) = 3637.7  4.4 MeV/c2
Small splitting from . OK when
coupled channel effects included.
•
Discovery of new narrow state(s)
above DD threshold X(3872) at
Belle (+ CDF, D0, BaBar).
M = 3872.0  0.6  0.5 MeV/c2
 2.3 MeV (90 % C.L.)
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What is the X(3872) ?
Charmonium
13D2 or 13D3.
D0D0* molecule.
Charmonium hybrid
(ccg).
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Hot Topics in Charmonium Spectroscopy – II
Observation of hc(1P1) by E835 and CLEO
CLEO
E835
pp hc c
e+e- 0hc c
hc c chadrons
M (hc )  3525.8  0.2  0.2 MeV / c 2 M (hc )  3524.4  0.9 MeV / c 2
C. Patrignani, BEACH04 presentation
A. Tomaradze, QWG04 presentation
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E 760 : M (hc )  3526.2  0.15  0.2 MeV / c
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Charmonium States above
the DD threshold
The energy region above the DD
threshold at 3.73 GeV is very poorly
known. Yet this region is rich in new
physics.
• The structures and the higher vector
states ((3S), (4S), (5S) ...)
observed by the early e+eexperiments have not all been
confirmed by the latest, much more
accurate measurements by BES.
• This is the region where the first radial
excitations of the singlet and triplet P
states are expected to exist.
• It is in this region that the narrow Dstates occur.
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Open Issues in Charmonium Spectroscopy
• All 8 states below threshold have been observed: hc evidence
stronger (E835, CLEO), its properties need to be measured
accurately.
• The agreement between the various measurements of the c mass
and width is not satisfactory. New, high-precision measurments are
needed. The large value of the total width needs to be understood.
• The study of the c has just started. Small splitting from the  must
be understood. Width and decay modes must be measured.
• The angular distributions in the radiative decay of the triplet P states
must be measured with higher accuracy.
• The entire region above open charm threshold must be explored in
great detail, in particular the missing D states must be found.
• Decay modes of all charmonium states must be studied in greater
detail: new modes must be found, existing puzzles must be solved
(e.g. -), radiative decays must be measured with higher precision.
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Charmonium at PANDA
• At 21032cm-2s-1 accumulate 8 pb-1/day (assuming 50 % overall
efficiency)  104107 (cc) states/day.
• Total integrated luminosity 1.5 fb-1/year (at 21032cm-2s-1, assuming
6 months/year data taking).
• Improvements with respect to Fermilab E760/E835:
– Up to ten times higher instantaneous luminosity.
– Better beam momentum resolution p/p = 10-5 (GSI) vs 210-4 (FNAL)
– Better detector (higher angular coverage, magnetic field, ability to detect
hadronic decay modes).
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Exotic light qq
The QCD spectrum is much richer than that of the quark
model as the gluons can also act as hadron components.
Glueballs states of pure glue
Hybrids qqg
•Spin-exotic quantum numbers JPC are
1-- 1-+
powerful signature of gluonic hadrons. 102
•In the light meson spectrum exotic
states overlap with conventional states.
•In the cc meson spectrum the density
of states is lower and the exotics can
1
be resolved unambiguously.
•1(1400) and 1(1600) with JPC=1-+.
Exotic cc
Hybrids and Glueballs
•1(2000) and h2(1950)
•Narrow state at 1500 MeV/c2 seen by 10-2
0
Crystal Barrel best candidate for
++).
glueball ground state (JPC=0D.
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4000 2
MeV/c
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Charmonium Hybrids
•
•
•
•
•
Bag model, flux tube model
constituent gluon model and LQCD.
Three of the lowest lying cc
hybrids have exotic JPC (0+-,1-+,2+-)
 no mixing with nearby cc states
Mass 4.2 – 4.5 GeV/c2.
Charmonium hybrids expected to
be much narrower than light hybrids
(open charm decays forbidden or
suppressed below DD** threshold).
Cross sections for formation and
production of charmonium hybrids
similar to normal cc states
(~ 100 – 150 pb).
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Excited gluon flux
P
CLEO
S
One-gluon exchange
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Charmonium Hybrids
•Gluon rich process creates
gluonic excitation in a direct way
Production
All Quantumnumbers
possible
– ccbar requires the quarks to annihilate
(no rearrangement)
– yield comparable to
charmonium production
Recoil
Meson
•2 complementary techniques
– Production
(Fixed-Momentum)
– Formation
(Broad- and Fine-Scans)
Formation
Quantumnumbers
like pp
•Momentum range for a survey
– p ~15 GeV
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Heavy Glueballs
Light gg/ggg systems are
complicated to identify (mixing).
Detailed predictions of mass spectrum
from LQCD
Exotic heavy glueballs:
• m(0+-) = 4140(50)(200) MeV
• m(2+-) = 4740(70)(230) MeV
Width unknown.
, , J/, J/ ...
Same run period as hybrids.
Morningstar und Peardon, PRD60 (1999) 034509
Morningstar und Peardon, PRD56 (1997) 4043
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Hadrons in Nuclear Matter
•Partial restoration of chiral symmetry in
nuclear matter
vacuum
– Light quarks are sensitive to quark condensate
•Evidence for mass changes of pions and
kaons has been deduced previously:
– deeply bound pionic atoms
– (anti)kaon yield and phase space distribution
•(cc) states are sensitive to gluon condensate
– small (5-10
in medium modifications for
low-lying (cc) (J/, c)
– significant mass shifts for excited states:
40, 100, 140 MeV/c2 for cJ, ’, (3770) resp.
nuclear medium


K
25 MeV

K+
100 MeV
MeV/c2)
K
D
•D mesons are the QCD analog of the H-atom.
– chiral symmetry to be studied on a single light
quark
– theoretical calculations disagree in size and sign
of mass shift (50 MeV/c2 attractive – 160 MeV/c2
repulsive)
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D
50 MeV
D+
Hayaski, PLB 487 (2000) 96
Morath, Lee, Weise, priv. Comm.
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Charmonium in Nuclei
•
•
•
Measure J/ and D production cross
section in p annihilation on a series of
nuclear targets.
J/ nucleus dissociation cross section
Lowering of the D+D- mass would allow
charmonium states to decay into this
channel, thus resulting in a dramatic
increase of width
(1D) 20 MeV  40 MeV
(2S) .28 MeV  2.7 MeV
Study relative changes of yield and
width of the charmonium states.
• In medium mass reconstructed from
dilepton (cc) or hadronic decays (D)
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The Detector
• Detector Requirements:
–
–
–
–
–
–
–
•
(Nearly) 4 solid angle coverage (partial wave analysis)
High-rate capability (2×107 annihilations/s)
Good PID (, e, µ, , K, p)
Momentum resolution ( 1 %)
Vertex reconstruction for D, K0s, 
Efficient trigger
Modular design
For Charmonium:
– Pointlike interaction region
– Lepton identification
– Excellent calorimetry
• Energy resolution
• Sensitivity to low-energy photons
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Panda Detector Concept
target spectrometer
straw tube
tracker
mini drift
chambers
forward spectrometer
muon
counter
DIRC
iron yoke
Solenoidal
magnet
electromagnetic
calorimeter
micro vertex
detector
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Timeline
• 2005 (Jan 15)
• 2005 (May)
• 2005-2008
•
•
•
•
2006
2009
2010
2011-2013
Technical Proposal (TP) with milestones.
Evaluation and green light for construction.
Project construction starts (mainly civil
construction).
Technical Design Report (TDR) according to
milestones set in TP.
High-intensity running at SIS18.
SIS100 tunnel ready for installation.
SIS100 commissioning followed by Physics.
Step-by-step commissioning of the full facility.
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Conclusions
The HESR at the GSI FAIR facility will deliver high-quality
p beams with momenta up to 15 GeV/c (√s  5.5 GeV).
This will allow Panda to carry out the following
measurements:
• High resolution charmonium spectroscopy in formation
experiments
• Study of gluonic excitations (glueballs, hybrids)
• Study of hadrons in nuclear matter
• Hypernuclear physics
• Deeply Virtual Compton Scattering and Drell-Yan
Hadron Physics has a brilliant future with PANDA at FAIR !
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