Paolo Lenisa Università di Ferrara and INFN - ITALY
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Transcript of Paolo Lenisa Università di Ferrara and INFN - ITALY
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P.Lenisa 1
Paolo LenisaUniversità di Ferrara and INFN - ITALY
Studying the hadron structure in DY-reactionsCERN – 27.04.10
Perspectives for Drell-Yan at FAIR
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2
100 m
UNILACSIS 18
SIS 100/300
HESR
SuperFRS
NESR
CRRESR
GSIGSI
FAIRFAIR
ESR
FLAIR
Rare-Isotope
Production Target
Antiproton
Production Target
CBM
PP& APHadron Structure, QCD & Medium Cooled antiprotons < 15 GeV, 500 users
Hadron Structure, QCD & Medium Cooled antiprotons < 15 GeV, 500 users
Nuclear Astrophys. NUSTARRI beam- fragmentation; 600 users
Nuclear Astrophys. NUSTARRI beam- fragmentation; 600 users
Warm Dense Plasmas Bunch-compression & Petawatt- Laser 250 users
Warm Dense Plasmas Bunch-compression & Petawatt- Laser 250 users
QCD-Phase Diagram: CBM HI beams 2 to 45 AGeV; 400 users
QCD-Phase Diagram: CBM HI beams 2 to 45 AGeV; 400 users
Materials Science, Space- and Radiation Biology(Ion- & antiproton- beams; 350 users
Materials Science, Space- and Radiation Biology(Ion- & antiproton- beams; 350 users
Fundamental SymmetriesUltra-High EM Fields SPARC; FLAIRAntiprotons, Hi-Z ions; 250 users
Fundamental SymmetriesUltra-High EM Fields SPARC; FLAIRAntiprotons, Hi-Z ions; 250 users
Accelerator Physics & Gym: Eight Rings & two Linacs
Accelerator Physics & Gym: Eight Rings & two Linacs
PandaPAX
P-Linac
FAIR – Research highlights
P.Lenisa DY at FAIR
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P.Lenisa 3
Antiprotons at FAIR
• Antiprotons with 1.5 GeV/c < p < 15 GeV/c• High luminosity: 2·1032 cm-2s-1
Thick targets: 4·1015 cm-2
Long beam life time: >30 min• High momentum resolution: p/p ≤ 4·10-5
Phase space cooling
HESR
DY at FAIR
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Hadron Physics „Dream Machine“ Asymmetric (double-polarized)
proton (15 GeV/c) – antiproton (3.5 GeV/c) collider
4P.Lenisa
pp
DY at FAIR
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P.Lenisa 5
Outline
• DY with polarized antiprotons @ asymmetric collider
• Perspectives for single-single spin asymm. @ fixed target
•Status of polarized antiprotons studies
DY at FAIR
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P.Lenisa 6
Transversity
- Probes relativistic nature of quarks- No gluon analog for spin-1/2 nucleon- Different evolution than - Sensitive to valence quark polarization
transversely polarisedquarks and nucleons
q1h
2Q q
Inclusive DIS Semi-inclusive DIS Drell-Yan
HERMES,COMPASS,JLab
h1 is chirally odd -> it needs a chirally odd partner
DY at FAIR
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The “golden-gate” to transversity:
P.Lenisa 7
,...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 *
Inclusive DIS Semi-inclusive DIS Drell-Yan
q q
q qqqqq
TTTT xqxqxqxqe
xhxhxhxheaA
)()()()(
)()()()(ˆ
dd
dd
21212
211121112
h1 from p-p Drell-Yan
DY at FAIR
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P.Lenisa 8
EXPERIMENT:Asymmetric collider:
polarized protons in HESR (p=15 GeV/c)polarized antiprotons in CSR (p=3.5 GeV/c)
Luminosity: 1.5x1031 cm-2s-1
s=200 GeV2
PAX proposal: Phase II
DY at FAIR
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p-pp-p
P.Lenisa 9
h1u from p-p Drell-Yan at PAX
PAX : s=x1x2~0.02-0.3 valence quarks (ATT large ~ 0.2-0.3 )
)()(
)()(ˆ
21
2111
xuxu
xhxhaA uuTTTT
q q
q qqqqq
TTTT xqxqxqxqe
xhxhxhxheaA
)()()()(
)()()()(ˆ
dd
dd
21212
211121112
• u-dominance• |h1u|>|h1d|
DY at FAIR
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10
Events for Drell-Yan processes
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 DY at FAIR
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11
s=45 GeV2s=210 GeV2
s=45 GeV2 s=210 GeV2
Cross-section
Asymmetry
P.Lenisa DY at FAIR
Shimizu et al. PRD71 (2005) 114007
Radiative corrections
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PAX Detector Concept
Physics: h1 distribution sin2 EMFF sin2
pbar-p elastic high |t|
Magnet: Keeps beam polarization vertical Compatible with Cerenkov Compatible with pol. 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 GEOMETRYLARGE ANGLES
Experiment: Flexible Facility
TOROIDNO FRINGE FIELD
e+e-
P.Lenisa DY at FAIR
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13
PAX Detector Concept
Designed for Collider but compatible with fixed target
Cerenkov(200 m)
(20 m)
GEANT simulation
P.Lenisa DY at FAIR
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14
-p Phase Space
Background peaks at * low energy * forward direction
acceptance
P.Lenisa DY at FAIR
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15
Background to Drell-Yan e+e-
10 min. experiment: 2∙108 p-pbar interactions several DY events
combinatorial+charm bckg
Background 1:1 to signal after PID, E>300 MeV, conversion veto, mass cut * the combinatorial component can be subtracted (wrong-sign control sample) * the charm can be reduced (vertex decay)
+-++ & --
P.Lenisa DY at FAIR
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16
Resolution
Vertex resolution high enoughto study charm background
Better than 2% mass resol * x dependence of h1
* resonance vs continuum
Mandatory to study M below J/ψ mass
P.Lenisa DY at FAIR
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17
10 % precision on the h1u (x) in the valence region
1 year of data taking at 15+3.5 GeV collider L = 1.5∙1031 cm-2s-1
p=0.8pbar=0.15
Precision in h1 measurement
p-pp-p
P.Lenisa DY at FAIR
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18
More statistics from J/…
eeqq
/Jqq unknown vector coupling, but same Lorentzand spinor structureas other two processes
Unknown quantities cancel in the ratios for ATT, but helicity structure remains!
Expected to double the statistics Good mass resolution fundamental
P.Lenisa DY at FAIR
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P.Lenisa DY at FAIR 19
CDM
(~CQSM)
2
1
GeVs 10
What about p-p?
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 )
A. Drago (2006)
Asymmetries are estimated to be large at PAX energies -> access to
)(_1xh
u
(Asymmetry evoluted under the assumption: ),(),( 2201 0QxqQxh
q
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P.Lenisa 20
p-p
DY events distribution (pp, pp and pd)
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-d
Extraction of h1d, h1q
for x<0.2
pppppd: complete mapping of transversity
DY at FAIR
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P.Lenisa 21
DYTTSIDISTT xfxf )p,()p,( 21
21
Test of Universality
A.V. Efremov et al.,
Phys. Lett. B 612, 233 (2005)
XeeppPAX :
y22/1 /
esMx M. Anselmino et al.,
Phys. Rev. D72, 094007 (2005)
XppE :704
XeepSIDIS :
Single spin asymmetries:Sivers function from pbar-p or pbar-p Drell-Yan @ PAX
DY at FAIR
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P.Lenisa 22
Fixed target experiments
DY at FAIR
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P.Lenisa 23
DY measurements @ PANDA
DY at FAIR
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P.Lenisa 24
•There is only a single self-sufficient process with a single polarized beam
•Single spin-asymmetry in pp or pp Drell-Yan
Measurement of Transversity
D. Boer, Ferrara (2008)
DY at FAIR
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P.Lenisa 25
A “window” to transversity: pbar - p l+l- X
Only self-sufficient single spin-asymmetry (involves TMDs)
analogue of BELLE cos2 asymmetry
Unpolarized DY production cross-section
analogue of SIDIS Collins asymmetry
Single-polarized DY production cross-section
DY at FAIR
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26
Kinematics and cross section
q
22
21
22
21
2q
212
2
F2
2
M,xqM,xqM,xqM,xqe)xx(sM9
4
dxdM
d•M2 = s x1x2 •xF=2QL/√s = x1-x2
M (GeV/c2)
22 GeV
collider
2 k events/day
fixed target
P.Lenisa DY at FAIR
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P.Lenisa 27
5x105 events
Luminosity = 2x1032cm-
2s-1 = 0.8 nbRate = 0.16 s-1
DY@PANDA: MC – Simulations IA. Bianconi NIM A593, 562 (2008)
1.5 < M2l+
l-<2.5
GeV2
qT>1 GeV/c60o< CS+<120o 1 < qT < 2 GeV/c
2 < qT < 3 GeV/c
Unpolarized case: p p +-X
M. Maggiora Univ. Torino and INFN (I)
DY at FAIR
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P.Lenisa 28
5x105 events
DY@PANDA: MC – Simulations II
1 < qT < 2 GeV/c2 < qT < 3 GeV/c
Single-spin asymmetry:
A. Bianconi, M. Radici Phys. Rev. D71, 074014 (2005)
p p +-X
(related to f1T) (related to h1T)
DY at FAIR
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P.Lenisa 29
A polarized target in PANDA?
Positioning:•Keep good PID for EM physics•No parasitic run possible
Technical issues:•Transport of polarized gas •Compensation of solenoidal field•Pumping of polarized gas
A very difficult task!
Possible options: •new detector with thoroidal field?•additional IP in HESR?
DY at FAIR
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P.Lenisa 30
Status of polarized antiproton-studies
DY at FAIR
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Polarized Antiprotons.Two Methods: Loss versus spin
flipFor an ensemble of spin ½ particles with projections + () and – ()
Paolo Lenisa P.Lenisa
31DY at FAIR
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Spin-filtering
Polarization build-up of an initially unpolarized particle beam by repeated passage through a polarized hydrogen target:
32P.LenisaDY at FAIR
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Spin-filtering at TSR: „FILTEX“ – proof-of-principle
→ Spin filtering works for protons!
F. Rathmann et al., PRL 71, 1379
(1993)
33P.Lenisa
PAX submitted new proposal to find out how well spin filtering works for antiprotons (CERN-SPSC-2009-012 / SPSC-P-337)
Polarization buildup process quantitatively understood!
•TSR spin filtering with protons:
σexp=73 ± 6 mb• Average theoretical value:
σtheo=86 ± 2 mb•Brief summary in: D.
Oellers et al., Phys. Lett. B 674, 269 (2009).
DY at FAIR
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P.Lenisa 34
PAX target section
Electron cooler
Siberian snake
PAX at the CERN-AD (spin filtering with antiprotons)
DY at FAIR
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P.Lenisa 35
Experimental Setup for AD
Atomic Beam Source
Six additional quadrupoles:-4 from COSY-2 from CELSIUS
Breit-RabiPolarimeter
Target chamber:Detector system + storage cell
DY at FAIR
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Spin-dependence of the pbar-p interaction
P.Lenisa 36
Model A: T. Hippchen et al., Phys. Rev. C 44, 1323 (1991).
Model OBEPF: J. Haidenbauer, K. Holinde, A.W. Thomas, Phys. Rev. C 45, 952 (1992).
Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995).
• Measurement of the polarization buildup equivalent to the determination of σ1 and σ2
• Once a polarized antiproton beam is available, spin-correlation data can be measured at AD (50-500 MeV)
DY at FAIR
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Spin-filtering studies at COSY- FZJ-Germany
ABS
BRP
COSY-Quadupoles
Low-β quadrupoles
Target chamber with storage cell
and detector system
P.Lenisa 37
Main purpose:1.Confirm understanding of spin-filtering with protons.2.Commissioning of the experimental setup for AD
Proposal to COSY PAC (submitted in July 2009)
Low-β magnet installation at COSY
(summer 2009)
DY at FAIR
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P.Lenisa 38
Low-b section commissioning (Feb. 2010)
Acceptance measurements with scrapers
Low- section does not limit the machine acceptance
DY at FAIR
New low- sectionOld lattice
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P.Lenisa 39
Conclusions
• Outstanding case for DY with polarized antiprotons
•Interesting perspectives for DY on fixed target•Polarized target in PANDA technical challenge
•Studies on polarized antiprotons undertaken by PAX Collab.
DY at FAIR
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P.Lenisa DY at FAIR 40
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P.Lenisa 41DY at FAIR
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Expected polarizations after filtering for two lifetimes at AD
transverse
A
D
42
P.Lenisa
longitudinal
DY at FAIR
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P.Lenisa 43
Higher energy p-p machine
GeVs 100
V. Barone, T. Calarco and A. Drago
Phys. Rev. D 56 (1997) 527
•s •Asymmetry
•ALL>ATT
•sJPARC idealDY at FAIR
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44
• Background higher for than for e
Background for Xeepp
Preliminary PYTHIA result (2109 events)
• Background from charge coniugated mesons negligible for e.
e
x1000
x100
Total background
x1000
x100
e
Background origin
P.Lenisa DY at FAIR
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P.Lenisa 45
The PANDA detector
DIRC
DY at FAIR
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P.Lenisa 46
From DY to elastic e+e- production:Proton Electromagnetic Form Factors
@fixed target
DY at FAIR
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P.Lenisa 47
Background in pbar-p e+e-
DY at FAIR
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P.Lenisa 48
DY with e+/e- @ PANDA?Pion-rejection promisiong...
F. Maas Univ. of Mainz – GSI (D)
DY at FAIR
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P.Lenisa 49
Pbar-p -> e+e-
Statistical projection for timelike FF @ PANDA
(GE=GM) F. Maas (Mainz+GSI)
DY at FAIR
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P.Lenisa 50
Measurement of GE and GM moduli @ PANDA
- Use of different angular dependence for GE and GM
2fb-1 (4 months @ 2x1032cm-2s-1)-Generated events:
F. Maas
DY at FAIR
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P.Lenisa 51
Single Spin Observables
• Contains imaginary part • Access relative phase
• Very sensitive to different models
A. Z. Dubnickova, S. Dubnicka, M.P. Rekalo Nuovo Cimento A109, 241 (1996)
S.J. Brodsky, C.E. Carlson, J.R. Hiller, D.S. Hwang PRD 69, 054022 (2004)
DY at FAIR
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P.Lenisa 52
•Most contain moduli GE, GM• Independent GE-GM separation• Test of Rosenbluth separation in the time-like region
•Access to GE-GM phase•Very sensitive to different models (next transparencies)
Double polarized pbar-p annihilation:
E. Tomasi, F. Lacroix, C. Duterte, G.I. Gakh, EPJA 24, 419(2005)
DY at FAIR