P. Lenisa The PAX project 1 Paolo Lenisa – Università and INFN – Ferrara, ITALY Trento, July 6...
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Transcript of P. Lenisa The PAX project 1 Paolo Lenisa – Università and INFN – Ferrara, ITALY Trento, July 6...
P. Lenisa The PAX project 1
Paolo Lenisa – Università and INFN – Ferrara, ITALY
Trento, July 6th 2006
http://www.fz-juelich.de/ikp/pax
PAXPAXPolarized Antiproton Polarized Antiproton
ExperimentsExperiments
P. Lenisa The PAX project 2
PAX CollaborationPAX Collaboration
TIMELINE
Jan. 04 Letter of Intent for FAIR
May 04 QCD-PAC meeting at GSI
Aug. 04 Workshop on polarized antiprotons at GSI
Jan. 05 Technical Proposal for FAIR
Mar. 05 QCD-PAC meeting at GSI
Nov. 05 LoI to CERN-SPSC to perform spin-filtering experiments with antiprotons at the AD ring
Apr. 06 LoI to COSY-PAC for spin filtering experiments with protons at COSY
180 physicists35 institutions (15 EU, 20 NON-EU)
P. Lenisa The PAX project 3
… the PAC would like to stress again the uniqueness of the program with polarized anti-protons and polarized protons that could become available at GSI.
Evaluation by QCD-PAC (March 2005)Evaluation by QCD-PAC (March 2005)
The STI requests R&D work to be continued on the proposed asymmetric collider experiment with both polarized anti-protons and protons:t o demonstrate that a high degree of anti-proton polarization can be reached
The STI believes that PAX should become part of the FAIR core research program based on its strong scientific merit once the open problems are convincingly solved.
Recommendation of the STI of FAIR Recommendation of the STI of FAIR (Sept. (Sept. 2005)2005)
P. Lenisa The PAX project 4
Physics MotivationsPhysics Motivations
P. Lenisa The PAX project 5
Physics with polarized antiprotons at GSI-PAX
Transversity via Drell-Yan processes
TTA direct access to transversity
Transverse Single Spin Asymmetries
QCD “theorem”: (Sivers)D-Y = – (Sivers)DISNA
Time-like e.l.m. form factors
llpp form factors
Elastic processes
SLSSLLNNN AAA AA , , ,, spin mysteries like in pp ?
High Energy
Low Energy
P. Lenisa The PAX project 6
h1 from pbar-p Drell-Yan at GSI
Similar predictions by Efremov et al.,
Eur. Phys. J. C35, 207 (2004)
PAX : M2s=x1x2~0.1-0.3 → valence quarks (ATT large ~ 0.2-0.4 )
Anselmino et al. PLB 594,97
(2004)
)()(
)()(ˆ
)()()()(
)()()()(ˆ
21
2111
21212
211121112
xuxu
xhxha
xqxqxqxqe
xhxhxhxheaA uu
TT
q q
q qqqqq
TTTT
P. Lenisa The PAX project 7
10 % precision on the h1u (x) in the valence region
1 year of data taking at 15+3.5 GeV collider L = 2∙1030 cm-2s-1
Precision in hPrecision in h11 measurement measurement
(L~1031 reachable)
P. Lenisa The PAX project 8
q q
q qqqqq
TTTT xqxqxqxqe
xhxhxhxheaA
)()()()(
)()()()(ˆ
dd
dd
21212
211121112
Barone, Calarco, Drago
Martin, Schäfer, Stratmann, Vogelsang
What about p-p?
h1q (x, Q2) small and with much slower evolution than
Δq(x, Q2) and q(x, Q2) at small x
h1q (x, Q2)- h1q (x, Q2)≠
RHIC: τ=x1x2~10-3 → sea quarks (ATT ~ 0.01 )
JPARC/U70: τ=x1x2~10-1 → valence and sea (ATT ~ 0.1 )
PAX: τ=x1x2~10-1 → valence and sea (ATT ~ 0.1 )
P. Lenisa The PAX project 9
DY in p-p: ADY in p-p: ATT TT
•Aymmetry is large at PAX energy (> 0.1)
•Sign of the asymmetry will distinguish between the two models.
•It will give indications about calculation of sea distributions.
),(),( 2201 0QxqQxh
q
),(),( 2201 0QxqQxh
q
1
2Asymmetries evoluted from the
assumptions:
CDM
(~CQSM)
2
1
GeVs 10
A. Drago
P. Lenisa The PAX project 10
pp-pbar-pbar
DY events distribution (√sDY events distribution (√s~15 GeV)~15 GeV)
p-pbar +p-p -> complete map of transversity
p-pp-p
Extraction of h1u for x>0.2x1=x2 ->ATT~h1u2
Direct measurement of h1u for 0.15<x<0.5
M2/s=x1x2~0.01-0.3
P. Lenisa The PAX project 11
Val. scenario
Std. scenarioxF=x1-x2
q q
q q
LLDYLL
xqxqxqxqe
xqxqxqxqeaA
21212
21212
DY in p-p: ADY in p-p: ALL LL
•Large asymmetries expected
•Test of the assumptions of the fits
GeVs 10
Models:
oAA CDMCQSM
LLLL
Val. scenario: 0;
),(
),(2
2
ss
d
u
xu
xd
ssdduuQxq seasea ),( 2
Std. scenario:
P. Lenisa The PAX project 12
Physics with polarized antiprotons at GSI-PAX
Transversity via Drell-Yan processes
TTA direct access to transversity
Transverse Single Spin Asymmetries
QCD “theorem”: (Sivers)D-Y = – (Sivers)DISNA
Time-like e.l.m. form factors
llpp form factors
Elastic processes
SLSSLLNNN AAA AA , , ,, spin mysteries like in pp ?
High Energy
Low Energy
P. Lenisa The PAX project 13
Single Spin Asymmetries (and their partonic
origin)
pq
Pq
π
k┴Collins effect = fragmentation of polarized quark
depends on Pq· (pq x k┴)
P
pk┴
Sivers effect = number of partons in polarized
proton depends on P · (p x k┴)
q
pk┴
Boer-Mulders effect = polarization of partons in
unpolarized proton depends on Pq · (p x k┴)
qPq
Collins: chiral-odd
Sivers: chiral-even
Boer-Mulders: chiral-odd
These effects may generate SSA
d d
d dNA
P. Lenisa The PAX project 14
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
P. Lenisa The PAX project 15
Physics with polarized antiprotons at GSI-PAX
Transversity via Drell-Yan processes
TTA direct access to transversity
Transverse Single Spin Asymmetries
QCD “theorem”: (Sivers)D-Y = – (Sivers)DISNA
Time-like e.l.m. form factors
llpp form factors
Elastic processes
SLSSLLNNN AAA AA , , ,, spin mysteries like in pp ?
High Energy
Low Energy
P. Lenisa The PAX project 16
pp Elastic Scattering from ZGSpp Elastic Scattering from ZGS
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
P. Lenisa The PAX project 17
Physics with polarized antiprotons at GSI-PAX
Transversity via Drell-Yan processes
TTA direct access to transversity
Transverse Single Spin Asymmetries
QCD “theorem”: (Sivers)D-Y = – (Sivers)DISNA
Time-like e.l.m. form factors
llpp form factors
Elastic processes
SLSSLLNNN AAA AA , , ,, spin mysteries like in pp ?
High Energy
Low Energy
P. Lenisa The PAX project 18
Proton Electromagnetic Proton Electromagnetic Formfactors Formfactors
• Single-spin asymmetry in pp → e+e-
– Measurement of relative phases of magnetic and electric FF in the time-like region
• 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)
P. Lenisa The PAX project 19
Experimental setupExperimental setup
P. Lenisa The PAX project 20
PAX Accelerator SetupPAX Accelerator Setup
• Antiproton Polarizer Ring (APR)• Asymmetric Antiproton-Proton Collider (CSR) • High Energy Synchrotron Ring (HESR)
P. Lenisa The PAX project 21
Antiproton Polarizer RingAntiproton Polarizer Ring
Energy 250 MeV
250 mm mrad
Circumf.
86 m
P. Lenisa The PAX project 22
Staging: Staging: Phase I (PAX@CSR)Phase I (PAX@CSR)
Physics: EMFFpbar-p elastic
Experiment: pol./unpol. pbar on internal polarized target
Independent from HESR running
P. Lenisa The PAX project 23
Staging: Staging: Phase II (PAX@HESR)Phase II (PAX@HESR)
EXPERIMENT:Asymmetric collider: polarized antiprotons in HESR (p=15 GeV/c)
polarized protons in CSR (p=3.5 GeV/c)
Physics: Transversity
Second IP with minor interference with PANDA
P. Lenisa The PAX project 24
Parameter Bunched Coasting
CSR HESR CSR HESR
Particles pbar p pbar p
Circum. [m] 183 574 183 574
Pmax [GeV/c] 3.65 15 3.65 15
smax [GeV2] ~ 200 ~ 200
No. bunches 10 30 - -
No. particles 5x1011 2.4x1012 5x1011 1x1013
Lifetime [hs] ~1500 ~300 ~1500 ~300
Lum. [cm-2s-
1]5x1030 1.2x1031
Polar. ↑↑,→→, ↑→ ↑↑,→→, ↑→
p-p yes yes
ParametersParameters
P. Lenisa The PAX project 25
Symmetric colliderSymmetric collider
Circum.[m] 681
No. Bunches 10
No. p 1x1012
No pbar 1x1012
Smax [GeV2] ~900
Polar. ↑↑,→→
p-p no
Asymm. collider
Luminosity
P. Lenisa The PAX project 26
PAX Detector Concept PAX Detector Concept Physics: h1 distribution sin2 EMFF sin2
pbar-p elastic high |t|
Detector: Extremely rare DY signal (10-7 p-pbar) Maximum Bjorken-x coverage (M interval) Excellent PID (hadron/e rejection ~ 104) High mass resolution (≤2 %)
Moderate lepton energies (0.5-5 GeV)
Azimuthally Symmetric:BARREL GEOMETRY
LARGE ANGLES
Experiment: Flexible Facility e+e-
P. Lenisa The PAX project 27
Kinematics for Drell-Yan processes
QCD corrections might be very large at smaller values of M, for cross-sections, not for ATT: K-factor almost
spin-independent H. Shimizu, G. Sterman, W. Vogelsang and H. Yokoya, hep-ph/0503270
V. Barone et al., in preparation
Fermilab E866 800 GeV/c
CERN NA51 450 GeV/c
"safe region"
/JMM
s
M J /2
Usually taken as
Q2>4 GeV2
P. Lenisa The PAX project 28
PAX Detector Concept PAX Detector Concept Physics: h1 distribution sin2 EMFF sin2
pbar-p elastic high |t|
Magnet: Keeps beam polarization vertical Compatible with Cerenkov Compatible with polarized target
Detector: Extremely rare DY signal (10-7 p-pbar) Maximum Bjorken-x coverage (M interval) Excellent PID (hadron/e rejection ~ 104) High mass resolution (≤2 %)
Moderate lepton energies (0.5-5 GeV)
Azimuthally Symmetric:BARREL GEOMETRY
LARGE ANGLES
Experiment: Flexible Facility
TOROIDNO FRINGE FIELD
e+e-
P. Lenisa The PAX project 29
PAX Detector Concept PAX Detector Concept
Designed for Collider but compatible with fixed target
Cerenkov(200 m)
(20 m)
GEANT simulation
P. Lenisa The PAX project 30
2011-2013 APR final design and construction
Phase I: 2014-2017
APR+CSR @ GSI
Physics: EMFF, p-pbar elastic with fixed target.
Phase II: 2018 - …
HESR+CSR asymmetric collider
Physics: h1
The The (long) (long) way towards away towards apolarized antiproton colliderpolarized antiproton collider
Phase 0: 2006-2010
Pol. buildup measurements @ COSY and CERN
P. Lenisa The PAX project 31
P. Lenisa The PAX project 32
SIS18 HESR
RESR
APR
CSR
CSR
HESR CSR
CSR
HESR
Antiproton and Proton accelerators’ scheme
Energy
time
proton
antiproton
P. Lenisa The PAX project 33
Higher energy p-p machineHigher energy p-p machine
GeVs 100
V. Barone, T. Calarco and A. Drago
Phys. Rev. D 56 (1997) 527
•s •Asymmetry
•√s @ PAX ideal
P. Lenisa The PAX project 34
Transverse seaTransverse sea
M. Wakamatsu and T. KubotaPhys. Rev. D 63 (1999) 034020
V. Barone, T. Calarco and A. Drago
Phys. Lett. B 390 (1997) 287
CDM CQSM
•The two models predict different sign for (with comparable amplitude).
uh
1
dh
1
),(1 initu
Qxh),(
1 evoluQxh
),(1 initd
Qxh),(
1 evoldQxh
uh
1
P. Lenisa The PAX project 35
Longitudinal seaLongitudinal sea
M. Glück et al.Phys. Rev. D 63 (2001) 094005
Models:
ouu CDMCQSM
ux
ux
dx
dx
sx
Gx
Val. scenario: 0;
),(
),(2
2
ss
d
u
xu
xd
ssdduuQxq seasea ),( 2
Std. scenario: