Physics with the PANDA Detector at GSI

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					    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

• 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

     D. Bettoni - Panda at GSI   3
 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                             •Radioactive beams
•Cooled beams                                      •e – A collider
•Rapidly cycling superconducting magnets           •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
• 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 γ-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
• δp/p~10-4 (stochastic cooling)

High resolution mode
• δp/p~10-5 (el. cooling < 8 GeV/c)
• Luminosity      = 1031 cm-2s-1

                              D. Bettoni - Panda at GSI   6
                The PANDA Collaboration
     More than 300 physicists from 48 institutions in 15 countries
U Basel               U & INFN Genova                  U Pavia
IHEP Beijing          U Glasgow                        IHEP Protvino
U Bochum              U Gießen                         PNPI Gatchina
U Bonn                KVI Groningen                    U of Silesia
U & INFN Brescia      U Helsinki                       U Stockholm
U & INFN Catania      IKP Jülich I + II                KTH Stockholm
U Cracow              U Katowice                       U & INFN Torino
GSI Darmstadt         IMP Lanzhou                      Politechnico di Torino
TU Dresden            U Mainz                          U Oriente, Torino
JINR Dubna            U & Politecnico & INFN           U & INFN Trieste
(LIT,LPP,VBLHE)       Milano                           U Tübingen
U Edinburgh           U Minsk                          U & TSL Uppsala
U Erlangen            TU München                       U Valencia
NWU Evanston          U Münster                        IMEP Vienna
U & INFN Ferrara      BINP Novosibirsk                 SINS Warsaw
U Frankfurt           LAL Orsay                        U Warsaw
LNF-INFN Frascati
                                  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.

           β2 ≈ 0.2 αs ≈ 0.3
     Non-relativistic potential models +
      Relativistic corrections + PQCD

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        Experimental Study of Charmonium

          e+e- annihilation                                pp annihilation
•  Direct formation only possible for        •   Direct formation possible for all
   JPC = 1-- states.                             quantum numbers.
• All other states must be produced          •   Excellent measurement of masses
   via radiative decays of the vector            and widths for all states, given by
   states, or via two-photon                     beam energy resolution and not
   processes, ISR, B-decay, double               detector-limited.
Good mass and width resolution for
the vector states. For the other states
modest resolutions (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:
         2J +1 π      Bin Bout ΓR
σ BW   =
           4 k 2 ( E − M R )2 + ΓR / 4

The production rate ν is a convolution of the
BW cross section and the beam energy distribution function f(E,∆E):
                 ν = L0 {ε ∫ dEf ( E , ∆E )σ BW ( E ) + σ b }
The resonance mass MR, total width ΓR 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 ηc(21S0) by Belle
     (+BaBar, CLEO).                                       ηc          η′c

     M(η′c) = 3637.7 ± 4.4 MeV/c2
     Small splitting from ψ′. OK when
     coupled channel effects included.

•    Discovery of new narrow state(s)                      What is the X(3872) ?
     above DD threshold X(3872) at                        !Charmonium
     Belle (+ CDF, D0, BaBar).                              13D2 or 13D3.
                                                           !D0D0* molecule.
    M = 3872.0 ± 0.6 ± 0.5 MeV/c2
                                                           !Charmonium hybrid
     Γ< 2.3 MeV (90 % C.L.)                                 (ccg).

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      Hot Topics in Charmonium Spectroscopy – II
             Observation of hc(1P1) by E835 and CLEO


                                                   e+e- →ψ′→π0hc →ηcγ→γγγ
        pp →hc →ηcγ→γγγ                           hc →ηcγ ηc→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

                E 760 : M ( hc ) = 3526.2 ± 0.15 ± 0.2 MeV / c               2

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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
• The structures and the higher vector
    states (ψ(3S), ψ(4S), ψ(5S) ...)
    observed by the early e+e-
    experiments 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 D-
    states 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
• The agreement between the various measurements of the ηc 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 η′c has just started. Small splitting from the ψ′ 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. ρ-π), 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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                    Hybrids and Glueballs
  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

                                                                          Exotic cc
                                                       Exotic light qq
•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.
•π1(1400) and π1(1600) with JPC=1-+.
•π1(2000) and h2(1950)
•Narrow state at 1500 MeV/c2 seen by 10-2
 Crystal Barrel best candidate for        0                    2000      4000 2
glueball ground state (JPC=0++).
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                      Charmonium Hybrids

•   Bag model, flux tube model                             Excited gluon flux
    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                                Σ
    suppressed below DD** threshold).
                                                           One-gluon exchange
•   Cross sections for formation and
    production of charmonium hybrids
    similar to normal cc states
    (~ 100 – 150 pb).

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                    Charmonium Hybrids

•Gluon rich process creates
gluonic excitation in a direct way                         All Quantumnumbers
 – ccbar requires the quarks to annihilate                 possible

   (no rearrangement)
 – yield comparable to
   charmonium production

•2 complementary techniques
 – Production
   (Fixed-Momentum)                                 Formation
 – Formation                                                like pp

   (Broad- and Fine-Scans)

•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.
φφ, φη, J/ψη, J/ψφ ...
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       nuclear medium
 – Light quarks are sensitive to quark condensate
•Evidence for mass changes of pions and                                              25 MeV
kaons has been deduced previously:                        π                             π+
 – deeply bound pionic atoms
 – (anti)kaon yield and phase space distribution          K
•(cc) states are sensitive to gluon condensate                                     100 MeV
 – small (5-10 MeV/c2) in medium modifications for
   low-lying (cc) (J/ψ, ηc)                                                            K−
 – significant mass shifts for excited states:
   40, 100, 140 MeV/c2 for χcJ, ψ’, ψ(3770) resp.         D
•D mesons are the QCD analog of the H-atom.                                          50 MeV
 – chiral symmetry to be studied on a single light                                      D+
                                                                Hayaski, PLB 487 (2000) 96
 – theoretical calculations disagree in size and sign           Morath, Lee, Weise, priv. Comm.
   of mass shift (50 MeV/c2 attractive – 160 MeV/c2
                                    D. Bettoni - Panda at GSI                                21
                      Charmonium in Nuclei

•   Measure J/ψ and D production cross
    section in p annihilation on a series of
    nuclear targets.
•   J/ψ 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
        ψ(1D) 20 MeV → 40 MeV
        ψ(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) 4π solid angle coverage (partial wave analysis)
     – High-rate capability (2×107 annihilations/s)
     – Good PID (γ, e, µ, π, K, p)
     – Momentum resolution (≈ 1 %)
     – Vertex reconstruction for D, K0s, Λ
     – 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                          forward spectrometer
        straw tube       mini drift        muon
          tracker        chambers         counter


iron yoke

magnet        electromagnetic     micro vertex
                 calorimeter       detector

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D. Bettoni - Panda at GSI   25

• 2005 (Jan 15)   Technical Proposal (TP) with milestones.
                  Evaluation and green light for construction.
• 2005 (May)      Project construction starts (mainly civil
• 2005-2008       Technical Design Report (TDR) according to
                  milestones set in TP.
•   2006          High-intensity running at SIS18.
•   2009          SIS100 tunnel ready for installation.
•   2010          SIS100 commissioning followed by Physics.
•   2011-2013     Step-by-step commissioning of the full facility.

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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
• High resolution charmonium spectroscopy in formation
• 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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