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Hadron Physics with PANDA. QCD well understood at high Q 2 Emergence of eff. DoF at low Q 2 Study of the strong interaction in the transition region P henomena appear that are hard to predict from QCD : e.g. confinement, nature of hadrons, hadronic masses….

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Hadron Physics with PANDA

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Hadron Physics with PANDA

  • QCD well understood at high Q2Emergence of eff. DoF at low Q2

  • Study of the strong interaction in the transition region

  • Phenomena appearthat are hard to predict from QCD: e.g. confinement, nature ofhadrons, hadronic masses…

J. Pumplin et al., JHEP 0207 (2002) 012


How Do We Study the Hadrons?

  • Hadron Structure: Hard (virtual) photons, typically accessed via leptons, allow us to measure the constituents- Generalized parton distribution- Drell-Yan processes- Time-like form factor of the proton

  • Hadron Spectroscopy:Excitation spectrum accesses rare quark/gluon configurations- Search for glueballs, hybrids, molecules, tetraquarks … - Baryon spectroscopy- In-medium effects

  • Hadron Interactions: Pion/Kaon reactions, as well as Hyperons and Hypernuclei provide information about the strong force- Double hypernuclei


Hadron Structure with Electromagnetic Probes


Time-Like &Space-Like EM Form Factors

SL

Space-like

  • Constraints:

  • GEp(0)=1

  • GMp(0)=μp

  • GEp(4mp²)= GMp(4mp²)

  • Asymptotics

  • |GE,M(q²)| ~ (q²)-²

e-

e-

TL

Time-like

q2<0

p

e-

q2>0

e+

p+p  e++e- + X

Unphysical region

p

p

p

_

Real FFs

Complex FFs

_

0

q2

e+p e+p

p+p ↔ e++e-

3.52 (GeV/c)2

  • (Phragmén-Lindelhöftheorem)

  • Imaginary part of Time-Like form factors vanishes for q²→+∞


Time-Like& Space-Like EM Form Factors

electron scattering

annihilation pp e+e-

q2 > 4mp2

-

e+e- pp (BES, Novosibirsk, PANDA)

e- scattering ( Jlab…. A2/Mainz)

100

From S. Pacetti, arXiv:1012.1232v1

Spacelike

10-1

Timelike

p

GM/μp

unphysical

10-2

10-3

-10

30

20

10

-30

0

-20

Dispersion relations:

q2 < 0


ProtonEM FormFactorsin Time-LikeRegion

_

Cross-sections: pp → e+e-

-

4mp2

_

angular distributions: pp →e+e-

FENICE+DM2 (e+e-)

-

BABAR: (e+e-pp)

-

(pp)

E835

LEAR (pp)

Geff

  • Geff: large error bars above 13 (GeV/c)2

  • |GE/GM| :

    • Inconsistent data abovethreshold

    • Lack of precise data above 5 (GeV/c)2

-


Extract Time-Like |GE| and |GM| for proton up to 14 (GeV/c)2

from lepton angular distributions in pp e+e- reaction

and measureGeff up to 30 (GeV/c)2

-

Goal of PANDA Measurements

-

  • Two major challenges:

  • Decrease of sensitivity to GE

    withincreasing q2

  • Hugehadronic background

  •  (pp +-) /  (pp e+e-) ~ 106

-

-


Counting Rate and Sensitivity to |GE|

~120 days, L = 2x1032cm-2s-1

Lint=2 fb-1

Statisticalerrorsonly

GE=0

GE=GM

GE=3GM

M. Sudolet al. EPJA 44 (2010) 373

Ntot=1.1 106 Ntot=64000Ntot=2000


_

q2 = 8.21 (GeV/c)2

2.4 106

s(p+p-)/s(e+e-)

1.5 105

cosqCM

Rejection of pp +-Background

parametrization of CERN data for p p → +-

s < 6 (GeV/c)2 : Legendre polynomial fits

s > 6 (GeV/c)2 :

countingrules (Ong et Van de Wiele, IPNO-DR-08-01)

or Reggetrajectories (idem, EPJA46 (2010) 291).

-

-

pp π+π-

New measurements of p p → +-

will be provided by PANDA (also important for pQCD mechanism studies)

-

?

s(p+p-)/s(e+e-)


Courtesy of S. Pacetti

E. Tomasi-Gustafsson and M.P. Rekalo, PLB504,291

E. Tomasi-Gustafsson, arXIv:0907.4442

Geff

PANDA

< 1% ~10% ~23% ~50%

Phragmèn-Lindelöf theorem ?

Time-Like Form Factor Measurement with PANDA : Estimates of Precision

L=2 fb-1

Sudol et al. EPJA 44 (2010) 373

PANDA

BES

BES

pQCD ?


Geff

< 1% ~10% ~23% ~50%

Time-Like Form Factor Measurement with PANDA : Estimates of Precision

L=2 fb-1

-VDM: F. Iachello et al., PLB43, 171 (1973)

…extended VDM, PRC66, 045501 (2002)

Egle Tomasi-Gustafsson et al., EPJA24 (2005) 419

Sudol et al. EPJA 44 (2010) 373

PANDA

PANDA

BES

BES

PANDA willbring

Precisedetermination of |GE|and | GM | up to 14 (GeV/c)2

Geff up to 30 (GeV/c)2 : transition towardsperturbative QCD

pQCD ?


2 Contributions and Radiative Corrections

Rosenbluth

method

Important role of 2

exchange and

radiative corrections

  • Advantage of annihilation reactions pp e+e-

    The e+ ande-angular distributions are measured in the sameexperiment

  • PANDA measurements are sensitive to oddcos  terms

    d/dcose ~ A (1+ b cosesin2 e + c cos2e+..) withb=5% or more

    (M. Sudol et al EPJA 44(2010) 373).

Polarization

measurements

?

No C-odd terms

contribution

C-odd terms

contribution

_


Hadron Spectroscopy with Antiproton Annihilation


Why Antiprotons?

  • difficult to make

  • BUT:

  • gluon rich process

  • gain ~2 GeV in annihilation, reduced momentum transfer

  • all fermion-antifermion quantum numbers accessible

  • very high resolution in formation reactions

  • high angular momentum accessible


c.f.

Only JPC = 1-- allowed in e+e- (to 1st order)

_

Particle production in pp collisions

Formation:

_

_

All JPC allowed for (qq) accessible in pp


Example: χc1,2

  • Invariant mass reconstruction depends

  • on the detector resolution ≈ 10 MeV

Formation:

Resonance scan: Resolution depends

on the beam resolution

[email protected] ≈ 240 keV

PANDA ≈ 30 keV


Charmonium Spectroscopy

_

  • open questionsbelow DD threshold: widths, branching

  • new „XYZ“ states (Belle, BaBar, CLEO, CDF, D0, …)

  • newdegreesoffreedom: molecules, tetraquarks, gluonicexcitations?

  • conventionalstatesabove DD

  • highLstates: access in pp but not in e+e-

_

_


New Charmonium-like Discoveries

in addition to many more open charm states


How can PANDA contribute?

ε = 32 %

S/N = 2

  • simulation studies for several channels and √s:

  • J/ψπ+π-,J/ψπ0π0, χcγJ/ψγγ, J/ψγ, J/ψη, ηcγ

  • direct formation in pp: line shapes !

  • d target: pn with p spectator tagging, e.g. Z-(4430)

_

_

C. Hanhartet al.,

PRD 76 (2007) 034007

E. Braaten, M. Lu,

PRD 77 (2008) 014029

J/yp+p-

_

_

_

D0D0p0

D0D*0

D0D*0

≈ 100 events/day

≈ 40 events/day

S/N =25

J/yp+p-


Beyond standard quark configurations

  • QCD allows much more than what we have observed:

Exotics:

Baryons

Mesons

may have JPC not allowed for qq

_

Courtesy C. Hanhart


_

Exotics production in pp collisions

  • Production: all JPC accessible

Hybrids

JPC exotic

Exotic JPC would be clear signal

G.Bali, EPJA 1 (2004) 1 (PS)


Open charm: The Dsspectrum

  • newnarrowstates Ds*(2317) and Ds*(2460) seenbyBaBar, Belle, CLEO

  • massessignificantlylowerthanquark model expectation

  • statesare just below DK and D*K threshold

  • interpretationunclear: DK/D*K molecules, tetraquarks, chiraldoublers, …?

D. Besson et al., Phys. Rev. D68, 032002 (2003)

B. Aubert et al., Phys. Rev. Lett. 90, 242001 (2003)

B. Aubert et al. (BaBarCollab.), Phys. Rev. D 74 (2006) 032007


Ds0*(2317) Theoretical Predictions


Method: Threshold Scan

  • reaction:

  • excitation function only depends on m and Γof Ds(2317)

  • experimental accuracy determined by beam quality (Δp, σp/p), not by detector resolution


Simulation Results: Energy Scan

Msum = Mmiss(Ds) + M(Ds)

G = 100 keV


Hadron Interactions: Double Strange Hypernuclei


Production Mechanism and Detection Strategy


Instrumentation


The PANDA Collaboration

517 Members from

67 Institutes

18 Countries

Australia, Austria, Belarus, China, France, Germany, India, Italy, Poland, Romania, Russia, Spain, Sweden, Switzerland, Thailand, The Netherlands, USA, UK


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