Experimental Study of the Strong Interaction at FAIR
Diego Bettoni
Istituto Nazionale di Fisica Nucleare, Ferrara
Lattice 2007Regensburg, 31 July 2007
D. Bettoni Physics at FAIR 2
Outline
• FAIR• HESR• PANDA Physics Program
– Charmonium Spectroscopy– Hybrids and Glueballs– Hadrons in Nuclear Matter– Hypernuclear Physics– Timelike Proton Form Factors
• The PANDA Detector• PAX Physics Program
– Transversity in Polarized Deep Inelastic Scattering– Single Spin Asymmetries– Timelike Proton Form Factors
• The PAX Detector Concept• Conclusions
D. Bettoni Physics at FAIR 3
FAIR at a glance
D. Bettoni Physics at FAIR 4
The FAIR Complex
Antiprotonproduction
100 TmSynchrotron
SIS100
Collector & CoolerRing
AccumulatorRing
Deceleration
Rare isotopeProduction &
separator
HighEnergy
Storage Ring
HESR&
PANDA
NewExperimentalStorage Ring
CompressedBarionicMatter
experiment
NESR
300 TmStretcher
Ring
SIS300
From existing GSIUNILAC & SIS18& new proton linac
+ Experiments:E-I colliderNuclear PhysicsAtomic PhysicsPlasma PhysicsApplied Physics
D. Bettoni Physics at FAIR 5
Technical Realization of FAIR
100 m
UNILAC
SIS 18
SIS 100/300
HESR
SuperFRS
NESR
CR
RESR
FLAIR
Accelerator Components & Key Characteristics
Ring/Device Beam Energy Intensity
SIS100 (100Tm) protons 30 GeV 4x1013
238U 1 GeV/u 5x1011 (intensity factor 100 over present)
SIS300 (300Tm) 40Ar 45 GeV/u 2x109
238U 34 GeV/u 2x1010
CR/RESR/NESR ion and antiproton storage and experiment rings
HESR antiprotons 14 GeV ~1011
Super-FRS rare-isotope beams 1 GeV/u <109
Radioactive Ion Production Target
Anti-Proton Production Target
Existing facility: provides ion-beam source and injector for FAIR
Existing facility: provides ion-beam source and injector for FAIR
New future facility: provides ion and anti-matterbeams of highest-intensity and up to high energies
New future facility: provides ion and anti-matterbeams of highest-intensity and up to high energies
Technical Realization of FAIR
D. Bettoni Physics at FAIR 6
Beam Intensity: - primary heavy-ion beam intensity increases by x 100 – x 1000 - secondary beam intensity increases by up to x 10000
Beam Energy: - heavy-ion energy : x 30
Beam Variety: - antiprotons - protons to uranium & radioactive ion beams
Beam Precision:- cooled antiproton beams
- intense cooled radioactive ion beams
Beam Pulse structure: - optimized for experiments: from dc to 50 ns
Parallel Operation: - full accelerator performance for up to four different and independent experiments and experimental programs
Unprecedented System Parameters at FAIR
D. Bettoni Physics at FAIR 7
High luminosity mode
High resolution mode
• p/p ~ 10 (electron cooling)• Lumin. = 1031 cm s
• Lumin. = 2 x 1032 cm s • p/p ~ 10 (stochastic cooling)
• Production rate 2x107/sec
• Pbeam = 1 - 15 GeV/c
• Nstored = 5x1010 p
• Internal Target
_
High-Energy Storage Ring
PANDA
D. Bettoni Physics at FAIR 9
Antiproton Physics Program
• Charmonium Spectroscopy. Precision measurement of masses, widths and branching ratios of all (cc) 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.
• 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
D. Bettoni Physics at FAIR 10
QCD Systems to be studied in Panda
D. Bettoni Physics at FAIR 11
Charmonium Spectroscopy
Charmonium is a powerful tool for theunderstanding of the strong interaction.The high mass of the c quark (mc ~ 1.5GeV/c2) makes it plausible to attempt a
description of the dynamical properties ofthe (cc) system in terms of non relativistic
potential models, in which the functionalform of the potential is chosen to reproduce
the known asymptotic properties of thestrong interaction. The free parameters in
these models are determined from acomparison with experimental data.
Non-relativistic potential models +Relativistic corrections + PQCD + LQCD
2 0.2 s 0.3
D. Bettoni Physics at FAIR 12
Experimental Study of Charmonium
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).
In general, the measurement of In general, the measurement of
sub-MeV widths not possible in esub-MeV widths not possible in e++ee--..
pp annihilation• Direct formation possible for all
quantum numbers.
• Excellent measurement of masses Excellent measurement of masses and widths for all states, given by and widths for all states, given by beam energy resolution and not beam energy resolution and not detector-limiteddetector-limited.
D. Bettoni Physics at FAIR 13
Experimental Method in pp Annihilation
4/412
22
2
2RR
RoutinBW
ME
BB
kJ
The cross section for the process: pp cc final stateis given by the Breit-Wigner formula:
The production rate is a convolution of theBW cross section and the beam energy distribution function f(E,E):
bBW EEEdEfL )(),(0
The resonance mass MR, total width R and product of branching ratiosinto the initial and final state BinBout can be extracted by measuring theformation rate for that resonance as a function of the cm energy E.
D. Bettoni Physics at FAIR 14
Example: c1 and c2 scans in Fermilab E835
1
2
D. Bettoni Physics at FAIR 15
c1 and c2 masses and widths
c1 E835E835 E760E760
M(MeV/c2) 3510.719 0.051 0.019 3510.60 0.09 0.02
(MeV) 0.876 0.045 0.026 0.87 0.11 0.08
B(pp)(J/)(eV) 21.5 0.5 0.6 0.6 21.4 1.5 2.2
c2 E835E835 E760E760
M(MeV/c2) 3556.173 0.123 0.020 3556.22 0.13 0.02
(MeV) 1.915 0.188 0.013 1.96 0.17 0.07
B(pp)(J/)(eV) 27.0 1.5 0.8 0.7 27.7 1.5 2.0
1 2
D. Bettoni Physics at FAIR 16
The c(11S0) Mass
M(c) = 2980.4 1.2 MeV/c2
Experiment Mass (MeV/c2)
CLEO 2981.8 1.3 1.5
BaBar 2982.5 1.1 0.9
E835 2984.1 2.1 1.0
BES 2977.5 1.0 1.2
Belle 2979.6 2.3 1.6
BES 2976.3 2.3 1.2
Mark III 2969 4 4
Crystal Ball 2984 2.3 4
PDG 2006
D. Bettoni Physics at FAIR 17
The c(11S0) Total Width
(c) = 25.5 3.4 MeV
PDG 2006
Experiment Width (MeV)
CLEO 24.8 3.4 3.5
BaBar 34.3 2.3 0.9
E835 20.4+7.7-6-7 2.0
BES 17.0 3.7 7.4
Belle 29 8 6
BES 11.0 8.1 4.1
E760 23.9+12.6-7.1
R704 7.0+7.5-7.0
Mark III 10.1+33.0-8.2
Crystal Ball 11.5 4.5
D. Bettoni Physics at FAIR 18
The c(21S0)
BaBar
PDG 2006M(c) = 3638 4 MeV/c2
(c) = 14 7 MeV
Belle
D. Bettoni Physics at FAIR 19
The hc(11P1)0
c /Jhpp
E760
E835
cch 2/4.06.04.3524)( cMeVhM c
CLEOe+e- 0hc
hc c chadrons
M(E835)=3525.80.2±0.2 MeV/c2
D. Bettoni Physics at FAIR 20
Charmonium States abovethe DD threshold
The energy region above the DDthreshold at 3.73 GeV is very poorlyknown. Yet this region is rich in newphysics.• The structures and the higher vector
states ((3S), (4S), (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.
D. Bettoni Physics at FAIR 21
The D wave states
• The charmonium “D states” are above the open charm threshold (3730 MeV ) but the widths of the J= 2 states and are expected to be small:
DDD 23,1
forbidden by parity conservation*
23,1 DDD forbidden by energy conservation
21D
23D
Only the (3770), considered to be largely 3D1 state, has been clearly observed. It is a wide resonance (((3770)) = 25.3 2.9 MeV) decayingpredominantly to DD. A recent observation by BES of the J/+- decaymode was not confirmed by CLEO-c.
D. Bettoni Physics at FAIR 22
New States above DD threshold
Y(3940)J/
eeJ/ X(3940)
c2’(2S)
eeY(4260) eeY(4320)
X(3872)J/
D. Bettoni Physics at FAIR 23
D. Bettoni Physics at FAIR 24
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
– the newly discovered states understood (cc, exotics, multiquark, ...)
– Confirm vector states observed in R
D. Bettoni Physics at FAIR 25
Charmonium at PANDA• At 21032cm-2s-1 accumulate 8 pb-1/day (assuming 50 % overall
efficiency) 104107 (cc) states/day.• Total integrated luminosity 1.5 fb-1/year (at 21032cm-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 210-4 (FNAL)– Better detector (higher angular coverage, magnetic field, ability to detect
hadronic decay modes).
• Fine scans to measure masses to 100 KeV, widths to 10 %.• Explore entire region below and above open charm threshold.• Decay channels
– J/+X , J/ e+e-, J/ +
– – hadrons– DD
D. Bettoni Physics at FAIR 26
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 glueHybrids qqg
Exoti
c lig
ht
Exoti
c cc
1 -- 1-+
0 2000 4000MeV/c2
10-2
1
102
•Spin-exotic quantum numbers JPC are powerful signature of gluonic hadrons.•In the light meson spectrum exotic states overlap with conventional states.•In the cc meson spectrum the density of states is lower and the exotics can be resolved unambiguously.1(1400) and 1(1600) with JPC=1-+.11(2000) and h(2000) and h22(1950)(1950)
•Narrow state at 1500 MeV/c2 seen by Crystal Barrel best candidate for glueball ground state (JPC=0++).
D. Bettoni Physics at FAIR 27
1(1400) – Proof of Exotic Wave (CB)Posit ive
(F it - D at a)
Nega tive
2 (F it - D at a)
5
5
no 1 in F it
1 in F it
2
a2
a2
a2
a2
0 1
1
2
2
3
3
GeV / c2 4
GeV / c2 4
0 1
1
2
2
3
3
GeV / c2 4
GeV / c2 4
0 1
1
2
2
3
3
GeV / c2 4
GeV / c2 4
0 1
1
2
2
3
3
GeV / c2 4
GeV / c2 4
Cr ystalB ar r el
m2 (
0 ) [G
eV2 /
c4 ]
m2(-) [GeV2/c4]
D. Bettoni Physics at FAIR 28
Charmonium Hybrids
• Bag model, flux tube model constituent gluon model and LQCD.
• Three of the lowest lying cc hybrids have exotic JPC (0+-,1-+,2+-)
no mixing with nearby cc 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 cc states
(~ 100 – 150 pb).
CLEO
One-gluon exchange
Excited gluon flux
D. Bettoni Physics at FAIR 29
Charmonium Hybrids
•Gluon rich process creates gluonic excitation in a direct way
– ccbar requires the quarks to annihilate (no rearrangement)
– yield comparable tocharmonium production
•2 complementary techniques– Production
(Fixed-Momentum)– Formation
(Broad- and Fine-Scans)
•Momentum range for a survey – p ~15 GeV
ProductionAll Quantumnumberspossible
RecoilMeson
FormationQuantumnumberslike pp
D. Bettoni Physics at FAIR 30
Glueballs
Detailed predictions of mass spectrumfrom quenched LQCD.
– Width of ground state 100 MeV– Several states predicted below 5
GeV/c2, some exotic (oddballs)– Exotic heavy glueballs:
• m(0+-) = 4140(50)(200) MeV• m(2+-) = 4740(70)(230) MeV• predicted narrow width
Can be either formed directly or produced in pp annihilation.Some predicted decay modes , , J/, J/ ...
Morningstar und Peardon, PRD60 (1999) 034509Morningstar und Peardon, PRD56 (1997) 4043
The detection of non-exotic glueballs is not trivial, as these states mix withThe detection of non-exotic glueballs is not trivial, as these states mix withthe nearby qthe nearby qq states with the same quantum numbers, thus modifying theq states with the same quantum numbers, thus modifying theexpected decay pattern.expected decay pattern.
D. Bettoni Physics at FAIR 31
The f0(1500)
Observed in pp annihilations
by Crystal Barrel (0, 00and 30 ) and Obelix
(+-0, K+K-0, KK0S ).
f0(1450) and a0(1370) also
observed in same channels.
Mixing between conventional
scalar mesons (0++) and
glueball state.
Evidence for tensor glueball at
2 GeV contradictory.
NNssggf
NNssggf
NNssggf
79.013.060.01370
62.037.069.01500
14.091.039.01710
0
0
0
2/161440 cMeVmG
D. Bettoni Physics at FAIR 32
Hadrons in Nuclear Matter•Partial restoration of chiral symmetry in nuclear matter
– 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
•(cc) states are sensitive to gluon condensate– small (5-10 MeV/c2) in medium modifications for
low-lying (cc) (J/, c)– significant mass shifts for excited states:
40, 100, 140 MeV/c2 for cJ, ’, (3770) resp.
•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)
vacuumvacuum nuclear mediumnuclear medium
K
25 MeV
100 MeV
K+
K
Hayaski, PLB 487 (2000) 96Morath, Lee, Weise, priv. Comm.
D
50 MeV
D
D+
D. Bettoni Physics at FAIR 33
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 (cc) or hadronic decays (D)
D. Bettoni Physics at FAIR 34
Multi-Strangeness Systems
Hypernuclei, systems where one (or more) nucleon is substituted by one (or more) hyperon, allow access to a whole set of nuclear states containing an extra degree of freedom: strangeness
The lighter single strangeness Λ-hypernuclei have been studied since 50 years allowing to test and define shell model parameters and ΛN interaction. ΛΛ-hypernuclei, -atoms Ω-atoms are described by more complicated approaches, but allows to have an insight to more complex nuclear systems containing strangeness (hyperon-star, strange-quark star,...)Experimental situation : ~35 Λ-hypernuclei established since 50 years ago. Only 6 ΛΛ-hypernuclei
NAGARA
H. Takahashi et al., PRL 87, 212502-1 (2001)
D. Bettoni Physics at FAIR 35
- capture:
- p + 28 MeV-
3 GeV/c
Kaons _
trigger
p_
2. Slowing down and capture
of insecondary
target nucleus
2. Slowing down and capture
of insecondary
target nucleus
1.Hyperon-
antihyperonproduction
at threshold
1.Hyperon-
antihyperonproduction
at threshold+28MeV
3. -spectroscopy
with Ge-detectors
3. -spectroscopy
with Ge-detectors
Production of Double HypernucleiProduction of Double Hypernuclei
-(dss) p(uud) (uds) (uds)
D. Bettoni Physics at FAIR 36
Proton Electromagnetic Form Factorsin the Timelike Region
The electromagnetic form factors of the proton in the time-like region
can be extracted from the cross section for the process:
pp e+e-
First order QED predicts:
Data at high Q2 are crucial to test the QCD predictions for the
asymptotic behavior of the form factors and the spacelike-timelike
equality at corresponding values of Q2.
*22
2*22
222
* cos14
cos12cos
Ep
M Gs
mG
xsc
d
d
D. Bettoni Physics at FAIR 37
The dashed line is the PQCD fit:
222 ln
ss
CG
p
M
E835 Form Factor Measurement
s
(GeV2)
102|GM|
(a)
102 |GM|
(b)
11.63
12.43
11.018.007.016.074.1
12.020.008.017.094.1
08.015.005.013.048.1
09.017.005.014.063.1
D. Bettoni Physics at FAIR 38
D. Bettoni Physics at FAIR 39
Form Factor Measurement in Panda
In Panda we will be able to measure the proton timelike form factors
over the widest q2 range ever covered by a single experiment, from
threshold up to q2=30 GeV2, and reach the highest q2.
• At low q2 (near threshold) we will be able to measure the form factors with high statistics, measure the angular distribution (and thus |GM| and |GE| separately) and confirm the sharp rise of the FF.
• At the other end of our energy region we will be able to measure the FF at the highest values of q2 ever reached, 25-30 GeV2, which is 2.5 larger than the maximum value measured by E835. Since the cross sections decrease ~1/s5, to get comparable precision to E835 we will need ~82 times more data.
• In the E835 region we need to gain a factor of at least 10-20 in data size to be able to measure the electric and magnetic FF separately.
D. Bettoni Physics at FAIR 40
Crossed-Channel Compton Scattering
H, E(x, ξ, t)
H, E(x, ξ, t)~ ~
γ* γ
non-perturbative QCD
perturbative QCD
Wide angle Compton scatteringfactorisation into hard amplitude(calculable in perturbative QCD)
and soft amplitude(information on parton distributions)
Reversed Deeply Virtual Compton Scattering
pp γγclear experimental signatureboth baryons in ground state
σ ≈ 2.5pb @ s ≈10 GeV2
L = 2·1032 cm-2 s-1→ 103 events per month
Identical diagramreversed
D. Bettoni Physics at FAIR 41
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, K0
s, – Efficient trigger– Modular design
• For Charmonium:– Pointlike interaction region– Lepton identification– Excellent calorimetry
• Energy resolution• Sensitivity to low-energy photons
D. Bettoni Physics at FAIR 42
Panda Detector
D. Bettoni Physics at FAIR 43
Target SpectrometerTarget Spectrometer
p of momentum from 1.5 up to 15 GeV/c 2 Tesla solenoid proton pellet target or gas jet target Micro Vertex Detector Inner Time of Flight detector Tracking detector: Straw Tubes/TPC DIRC Electromagnetic Calorimeter Muon counters Multiwire Drift Chambers
D. Bettoni Physics at FAIR 44
Forward SpectrometerForward Spectrometer
Multiwire Drift Chambers/ Straw tubes deflecting dipole: 2 Tesla·meter Forward DIRC and RICH Forward Electromagnetic Calorimeters Time of Flight counters Hadron Calorimeter
D. Bettoni Physics at FAIR 45
Collaboration
• At present a group of 350 physicists from 47 institutions of 15 countries
Basel, Beijing, Bochum, Bonn, IFIN Bucharest, Catania, Cracow, Dresden, Edinburg, Erlangen, Ferrara, Frankfurt, Genova, Giessen, Glasgow, GSI, Inst. of Physics Helsinki,
FZ Jülich, JINR Dubna, Katowice, Lanzhou, LNF, Mainz, Milano, Minsk, TU München, Münster, Northwestern,
BINP Novosibirsk, Pavia, Piemonte Orientale, IPN Orsay, IHEP Protvino, PNPI St. Petersburg, Stockholm,
Dep. A. Avogadro Torino, Dep. Fis. Sperimentale Torino, Torino Politecnico, Trieste, TSL Uppsala, Tübingen,
Uppsala, Valencia, SINS Warsaw, TU Warsaw, AAS Wien
Basel, Beijing, Bochum, Bonn, IFIN Bucharest, Catania, Cracow, Dresden, Edinburg, Erlangen, Ferrara, Frankfurt, Genova, Giessen, Glasgow, GSI, Inst. of Physics Helsinki,
FZ Jülich, JINR Dubna, Katowice, Lanzhou, LNF, Mainz, Milano, Minsk, TU München, Münster, Northwestern,
BINP Novosibirsk, Pavia, Piemonte Orientale, IPN Orsay, IHEP Protvino, PNPI St. Petersburg, Stockholm,
Dep. A. Avogadro Torino, Dep. Fis. Sperimentale Torino, Torino Politecnico, Trieste, TSL Uppsala, Tübingen,
Uppsala, Valencia, SINS Warsaw, TU Warsaw, AAS Wien
http://www.gsi.de/panda
Austria – Belaruz - China - Finland - France - Germany – Italy – Poland – Romania - Russia – Spain - Sweden – Switzerland - U.K. – U.S.A..
PAX
D. Bettoni Physics at FAIR 47
Polarized Antiproton eXperiments
Cerenkovpppp
Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target
Proton EFFs
eepp
pbar-p elastic
Nucleon structure: polarized reactions
Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15
GeV/c) polarized protons in CSR (p=3.5
GeV/c)
Parton distribution: transversity
Xeepp
Drell-Yan
Charmonium
XJpp /
SSA
XllDXpp ,
D. Bettoni Physics at FAIR 48
Nucleon Structure and Transverse Spin Effects
transversely polarisedquarks and nucleons
h1(x): helicity flip chiral-odd needs a chiral odd partner
q1h q1f q1g
unpolarised quarksand nucleons
longitudinally polarised quarks and nucleons
HERMES,COMPASS,JLab PAX,RHIC,Jparc
Inclusive DIS Semi-inclusive DIS Drell-Yan
h1xh1h1xH1
т
D. Bettoni Physics at FAIR 49
Drell-Yan
,...d,d,u,uq
M invariant Massof lepton pair /2 / 2
2121 sQxsMxxxxx LFF
)( )()( )(1
9
42121
2
212
2
2
2
xqxqxqxqexxsMdxdM
d
F
sM 2
llqq *
GeV2
D. Bettoni Physics at FAIR 50
h1 from pp Drell-Yan
Similar predictions by Efremov et al., Eur. Phys. J. C35, 207 (2004)
PAX : s=x1x2~0.02-0.3 valence quarks (ATT large ~ 0.2-0.3 )
)()(
)()(ˆ
21
2111
xuxu
xhxhaA uu
TTTT
Anselmino et al. PLB 594,97
(2004)
q q
q qqqqq
TTTT xqxqxqxqe
xhxhxhxheaA
)()()()(
)()()()(ˆ
dd
dd
21212
211121112
• u-dominance• |h1u|>|h1d|
1year run: 10 % precision on the h1u(x) in the valence region
Pp=10%Pp=30%
D. Bettoni Physics at FAIR 51
h1 from pp Drell-Yan
Barone, Calarco, Drago
Martin, Schäfer, Stratmann, Vogelsang
h1q (x ,Q2)
h1q (x, Q2) small and with much
slower evolution than
Δq(x, Q2) and q(x, Q2) at small x
- h1q (x, Q2)≠
RHIC: M2/s=x1x2~10-3 → sea quarks (ATT ~ 0.01
)JPARC/U70: M2/s=x1x2~10-1-10-2 → valence and sea (ATT ~ 0.1 )PAX: M2/s=x1x2~10-1-10-2 → valence and sea (ATT ~ 0.1 )
)()(
)()(ˆ
)()()()(
)()()()(ˆ
21
2111
21212
211121112
xuxu
xhxha
xqxqxqxqe
xhxhxhxheaA uu
TT
q q
q qqqqq
TTTT
D. Bettoni Physics at FAIR 52
DY Event Distribution
p-pp-p
At x1=x2 ATT ~ h1u2
Direct measurement of h1u for 0.05<x<0.5
M2/s = x1x2 ~ 0.02-0.3
p-p, p-dp-p, p-d
Extraction of h1d, h1q
for x<0.2
pppppd: complete mapping of transversity
D. Bettoni Physics at FAIR 53
Single Spin Asymmetries
pq
Pq
π
k┴Collins effect = fragmentation of polarized quark
depends on Pq· (pq x k┴)
Chiral-Odd
Sivers effect = number of partons in polarized
proton depends on P · (p x k┴)
Chiral-Even
P
pp
k┴
q
k┴
qPq
pp
Boer-Mulders effect = polarization of partons in
unpolarized proton depends on Pq · (p x k┴)
Chiral-Odd
These effects may generate SSA
d d
d dNA
pq
P
k┴Polarizing FF = polarization of hadrons from
unpolarized partons depends on P · (pq x k┴)
PDFs
FFs
D. Bettoni Physics at FAIR 54
BNL-AGS √s = 6.6 GeV 0.6 < pT < 1.2 p↑p
E704 √s = 20 GeV 0.7 < pT < 2.0 p↑p
STAR-RHIC √s = 200 GeV 1.1 < pT < 2.5 p↑p
E704 √s = 20 GeV 0.7 < pT < 2.0 p↑p
SSA, pp → πX
D. Bettoni Physics at FAIR 55
The Sivers Function
M. Anselmino et al.,
Phys. Rev. D72, 094007 (2005)
DYTTSIDISTT xfxf )p,()p,( 21
21
Test of Universality
A.V. Efremov et al.,
Phys. Lett. B 612, 233 (2005)
XeeppPAX :
y22/1 / esMx
XppE :704
XeepSIDIS :
D. Bettoni Physics at FAIR 56
The Sivers Function
No Collins effect U.D’Alesio and F. Murgia
hep-ph/0612208
DXpp DXpp
Xpp ccqq
No fragmentation process
D. Bettoni Physics at FAIR 57
Proton Electromagnetic Form Factors
(Phys. Rev.C 68 (2003) 034325)
JLab PT data
SLAC RS data
TWO DIFFERENTS METHODS
TWO DIFFERENTS RESULTS
COMPARISON BETWEEN
ROSENBLUTH SEPARATION AND
POLARIZATION TRANSFER TECHNIQUES
D. Bettoni Physics at FAIR 58
Proton Timelike Form Factors
• Double-spin asymmetry in pp → e+e-
– independent GE-Gm separation
– test of Rosenbluth separation in the time-like region
2
p2
2E
22M
2M
*E
y
m4/q
/|G|)(sin|G|)(cos1
)GGIm()2sin(A
S. Brodsky et al., Phys. Rev. D69 (2004)
• Single-spin asymmetry in pp → e+e-
Measurement of relative phasesof magnetic and electric FF inthe time-like region
D. Bettoni Physics at FAIR 59
pp,pd,pp beams are pp,pd,pp beams are possiblepossible• APR: Antiproton Polarizer Ring (Ppbar>0.2)
• CSR: Cooled Synchrotron Ring ( p<3.5 GeV/c)
• HESR: High Energy Synchrotron Ring (p<15 GeV/c)
Asymmetric collider Luminosity up to 5·1031 cm-2s-1
D. Bettoni Physics at FAIR 60
PAX Detector Concept
Designed for Collider but compatible with fixed target
(200 m)
(20 m)
GEANT simulation
D. Bettoni Physics at FAIR 61
Polarized Antiproton Experiments
Phase I: Proton time-like FFs Hard pbar-p elastic scatt.
Fixed target experiment (√s<2 GeV): pol./unpol. pbar beam (p<4 GeV/c) internal H polarized target
Phase II: Transversity Distribution
Asymmetric collider (√s=15 GeV): polarized antiprotons in HESR (p=15
GeV/c) polarized protons in CSR (p=3.5
GeV/c)
D. Bettoni Physics at FAIR 62
Antiproton PolarizationThe polarization of antiprotons is based on the Spin Filtering method (interaction of unpolarized antiprotons with a polarized hydrogen target). This technique has been experimentally tested in 1992 (Filtex experiment) and it works, but:
1. Controversial interpretations of FILTEX experiment• Further experimental tests necessary• How does spin-filtering works?• Which role do electrons play? Tests with protons at COSY
2. No data to predict polarization from filtering with antiprotons. Measurements with antiprotons at AD/CERN
Fall 2007 Technical proposal to COSY-PAC for spin filtering
Technical proposal to SPSC for spin filtering at AD
2007-2008 Depolarization studies
2008-2009 Design and construction phase
2009-2010 Spin-filtering studies at COSY
Commissioning of AD experiment
2010 Installation at AD
2010-2011 Spin-filtering studies at AD
D. Bettoni Physics at FAIR 63
Summary and Outlook:Spectroscopy at FAIR
PANDAHigh-intensity cooled antiproton beams
High precision spectroscopy from s 2.25 GeV to 5.5 GeV:• charmonium• hybrids and glueballs• multiquark• mesons and hadrons• open charm
D. Bettoni Physics at FAIR 64
Summary and Outlook:Nucleon Structure at FAIR
PANDA• Proton Timelike Form Factors
– Very high-statistics measurement near threshold
– Measure angular distribution |GE|/|GM|
– Extend q2 range to 20-25 GeV2
PAX• Transversity in polarized pp DY• Single Spin Asymmetries and Sivers Function• Proton Timelike Form Factors
– Measurement with polarized beams
– Single- and double-spin observables
– Moduli and phases of TL form factors
D. Bettoni Physics at FAIR 65
Recent decision by German Minister Ms. Schavan:
Start of the International FAIR Project
on November 7, 2007
together with all partners that have expressed their commitment on FAIR.
Backup Slides
D. Bettoni Physics at FAIR 67
FAIR Schedule
D. Bettoni Physics at FAIR 68
Transversity and Tensor Charges
Soffer inequality M. Anselmino et al.
hep-ph/0008186
Transversity
u≈ 0.39, d≈-0.16
Tensor charges
M. Wakamatsu
arXiv: 0705.2917
D. Bettoni Physics at FAIR 69
Elastic Scattering
Spin-dependence at large-PSpin-dependence at large-P (90°90°cmcm):):
Hard scattering takes Hard scattering takes place only with spins place only with spins ..
D.G. Crabb et al., PRL 41, 1257
(1978)
T=10.85 GeV
Similar studies in pp elastic scattering
High-t pp from ZGS, AGSHigh-t pp from ZGS, AGS
Low-E pp, pd at ADLow-E pp, pd at AD
Polarization build-up studies
70
Principle of spin filter methodPrinciple of spin filter methodP beam polarizationQ target polarizationk || beam direction
σtot = σ0 + σ·P·Q + σ||·(P·k)(Q·k)
transverse case:
Q0tot
longitudinal case:
Q)( ||0tot
For initially equally populated spin states: (m=+½) and (m=-½)
Unpolarized anti-p beam
Polarized H target