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Perspectives for Polarized Antiprotons (PAX: a brief history)
Paolo LenisaUniversità di Ferrara and INFN
44100 – Ferrara - ITALY
P.Lenisa PAX story 1
ANKE-PAX WorkshopGatchina, June 25-27 2012
We have proposed a method to polarize antiprotons by „spin-filtering“
2PAX story
The beginning (2005)
P.Lenisa
High Energy Storage Ring (HESR) for a
beam of antiprotons
3PAX storyP.Lenisa
PAX Proposal to FAIR (2005)178 Collaborators
36 institutions (15 EU, 21 NON-EU)
P.Lenisa PAX story 4
Polarized antiprotons will pave the way to novel double (and single) spin observables:
* Proton-spin structure:Complete map of transversity Flavour separation
* Electromagnetic Form FactorsIndependent extraction of moduli of GE-GM in Time-Like regionTest of the Rosenbluth separation in TLMeasurement of the phase
* Hard p-pbar scatteringAdditional measurement in one of the most intriguing puzzles of HF
* Hadron spectroscopy
* Low-t pbar-p scatteringSpin and isospin dependence of nucleon-antinucleon interaction at low energy
Physics with Polarized Antiprotons
P.Lenisa PAX story 5
,...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 Drell-Yan
P.Lenisa PAX story 6
Phase I: Fixed target experiments in CSR
direction of
antiprotons
Physics: EMFF pbar-p elastic
Independent from HESR running
pol./unpol. Antiprotons in CSR 0.2 Gev/c<p<2.5 GeV/cpolarized internal proton target
(antiprotons)
P.Lenisa PAX story 7
Phase II: Asymmetric Proton-Antiproton Collider
direction of
protons
direction of
antiprotons
Physics: Transversity EMFF pbar-p elastic
polarized antiprotons in HESR (p=15 GeV/c)
polarized protons in CSR (p=3.5 GeV/c)
P.Lenisa PAX story 8
Antiproton Polarizer Ring (APR)
Ring Parameter
Beam energy 250 MeV
Number of antip. 1012
Ring acceptance 250 mm
mrad
Betatron ampl. at IP
< 0.3m
Ring circumference
86,5 m
Snake strength 2.4 Tm
Injection/Extraction Target
Electron Cooler Snake
Ion-optics at IPAtomic Beam Source (ABS)
parameter
ABS flow in feeding tube
1,5·1017 /s
Storage cell length 40 cm
Feeding tube diameter length
1 cm 15 cm
Long. holding field 300 mT
Electron polarization 0.9
Cell temperature 100 K
Final configuration after spin-filtering studies
P.Lenisa PAX story 9
… 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)
The STI requests R&D work to be continued on the proposed asymmetric collider experiment with both polarized anti-protons and protons:
-to demonstrate that the required luminosity for decisive measurements can be reached (->accomplished)
- to demonstrate that a high degree of anti-proton polarisation 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 (Sept. 2005)
P.Lenisa PAX story 10
Luminosity Considerations for Collider Mode
Particle species
Momentum / GeV/c
Number of bunches
Total number of particles
Beam lifetime / h
Peak luminosity / cm-2 s-1
CSR HESR
protons antiproton
3.65 15
10 30
1012 3·1011
~ 45 ~ 800
1.6·1030
CSR HESR
antiprotons
proton
3.65 15
- -
0.02 0.006
~ 1500 ~ 300
1.2·1031
“old”
“new”
Antiprotons in HESR -> protons
Bunched beams -> coasting
L>1031s-
1cm-2
2006: I milestone for PAX
P.Lenisa PAX story 11
Intense beam of polarized antiprotons was never produced:
•Conventional methods (ABS) not appliable
•Polarized antiprotons from antilambda decay • I < 1.5∙105 s-1 (P ≈ 0.35)
•Antiproton scattering off liquid H2 target• I < 2∙103 s-1 (P ≈ 0.2)
Little polarization from pbarC scattering exp’ts at LEAR
•Stern-Gerlach spin separation in a beam (never tested)
Spin filtering is the only succesfully tested technique
Polarized Antiprotons
How to produce polarized antiprotons?Spin-filtering
P.Lenisa
Polarization build-up of a circulating particle beam by interaction with a polarized gas target
12
P.Lenisa PAX story 13
Experimental SetupExperimental Setup ResultsResults
F. Rathmann. et al., PRL 71, 1379 (1993)
T=23 MeV
Low energy pp scattering
1<0 tot+<tot-
Expectation
Target Beam
1992 Filter Test at TSR with protons
P.Lenisa PAX story 14
1994 Meyer and Horowitz: three distinct effects1. Selective removal through scattering beyond θacc=4.4 mrad (σR=83
mb)2. Small angle scattering of target prot. into ring acceptance (σS=52
mb)3. Spin-transfer from pol. el. of target atoms to stored prot. (σE=-70 mb)
σ1= σR+ σS + σE = 65 mb
2005 Milstein & Strakhovenko + Nikolaev & Pavlov: only one effectOnly pp elastic scattering contributesNo contribution from other two effects σ1 = 85.6 mb
Observed polarization build-up: dP/dt = ± (1.24 ± 0.06) x 10-2 h-1
P(t)=tanh(t/τ1), 1/τ1=σ1Qdtf
σ1 = 72.5 ± 5.8 mb
Two interpretations of FILTEX result (2006)
P.Lenisa PAX story 15
Spin Filtering works, but:
1. Controversial interpretations of FILTEX experiment• Further experimental tests necessary
• Which role do electrons play?• How does spin filtering work?
Tests with protons at COSY
2. No data to predict polarization from filtering with antiprotons Measurements with antiprotons at AD/CERN
Spin Filtering: Status in 2006
P.Lenisa PAX story 16
Eur. Phys. J. A 34, 447 (2007)
A new idea (2007)
ep spin flip studies at COSY (2008)
• Use proton beam and co-moving electrons
• Turn experiment around: p e → p e into p e → p e
i.e. observe depolarization of a polarized proton beam
COSY electron cooler
(detuned)
Velocity mismatch
17PAX storyP.Lenisa
P.Lenisa PAX story 18
Principle of the Depolarization Measurementusing co-moving electrons of the e-cooler (COSY-2008)
Nominal CoolerVoltage
Tnominal = 100 s
Detuned CoolerVoltage
Tdetuned= 50 s
D2 Target onEcool on
D2 Target offEcool on/detuned
2T
T
uneddet
alminno
Eh = 0.001 MeVΔV = 235 V
ep spin flip cross section at COSY
No effect observed: measured cross sections at least 6 orders-of-magnitude smaller than predicted 1013 b
19PAX story
0
4107
|Relative velocity of electrons in proton rest frame| (c)
dep
ol (
barn
)
Nominal proton energy in electron rest frame (keV)0 1 2 3
0 110-3 210-3 310-3
2107
-2107
-4107
D.Oellers et al., Physics Letters B 674 (2009) 269
Meanwhile, Mainz group discovered numerical problems in the calculation → two errata.
P.Lenisa
2008: II milestone for PAX
PAX at the AD (2009)
PAX story 20
PAX target section
Electron cooler
Siberian snake
Status in 2009:•No contribution from EM interaction to polarization buildup.
• Spin-filtering only viable option• Spin-dependence of pbar-p interaction unknown
•“Warm” solution for AD lattice
P.Lenisa
Spin-dependence of the pbar-p interaction
21
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)
P.Lenisa PAX story
PAX story 22
Additional calculations…
PLB 690 (2010)
P.Lenisa
Cross sections
Projected polarizations
PAX story
Stages of installation at AD
P.Lenisa 23
2010 20112012
Phase 1
Phase 2
Phase 3
Installation of six magnets for the low-β insertion
Spin-filtering measurements up to 70
MeV with transverse beam polarization
Installation of the target chamber: Machine
acceptance studies. Stacking studies
P.Lenisa PAX story 24
The CERN Saga: PAX requests• Oct. 2009 PAX request to start phase I of installation not interfering with other experiments.
• Jan. 2010 PAX informs SPSC of acknowledgement of ERC grant.
• Jan.. 2011Meeting with Heuer• Apr. 2011: PAX sends a draft to SPSC Committee with the successful result of commissioning of single elements of experimental apparatus and request to start installation of phase I in Winter 2011 shutdown, to initiate machine studies in 2012 and to avoid conflicts with ELENA installation during 2013 shutdown.
• Mar. 2012PAX sends to SPSC Committee a draft with the results of spin-filtering studies.
P.Lenisa PAX story 25
The CERN Saga: SPSC answer• Oct. 2009 unofficial response from the SPS Committee:… Taking into account the timeline and constraints of the various projects concerned, the SPSC encourages the PAX Collaboration to first perform their spin filtering measurements at COSY, and to report these to the Committee, following which the SPSC will further review the proposal.
• Jan. 2010 Valle’s comment to ERC grant communicationCongratulation for getting approval of an ERC advanced grant… The comments by many of the referees on the risk and schedule issues of your project confort me in the prudent attitude of the SPSC in respect with the necessary related AD modification … Looking forward to the PAX filtering measurements at COSY to proceed further with your review!
• Jan.. 2011Meeting with Heuer• Apr. 2011: SPSC 101 recommendation:The SPSC received a report by the PAX collaboration describing the progress of their program at COSY The SPSC remains concerned by the impact of PAX on the AD antihydrogen programme, the risk factors and manpower requirements for implementing the PAX apparatus at the AD. The Committee considers any installation before the long shutdown to be premature.The Committee is looking forward to the results of the spin filtering measurements.
• Mar. 2012Draft sent to SPSC with final results of August-October 2011 beamtime• Apr. 2012 mail from Vallee.We were pleased to see that you finally succeeded to perform a spin filtering measurement at COSY, showing good control of your apparatus as well as theoretical understanding of spin filtering for protons. However inbetween many positive developments have occured at the AD, leading to an updated program for the coming years which is very constrained on both the scientific and logistic points of view. We consider that PAX is now incompatible with this program.
P.Lenisa PAX story 26
PAX gets acknowledgment in the community:EU – grants
• 2008-2011 – I3HP2 WP25 (PolAntiP)• Depolarization studies• Transverse spin-filtering at COSY
• 2012-2014 – I3HP3 WP25 (PolAntiP)• Longitudinal spin-filtering at COSY
• 2010-2015 – Advanced Resarch Grant POLPBAR
P.Lenisa PAX story 27
The CERN Saga: PAX requests• Oct. 2009 PAX request to start phase I of installation not interfering with other experiments.
• Jan. 2010 PAX informs SPSC of acknowledgement of ERC grant.
• Jan.. 2011Meeting with Heuer• Apr. 2011: PAX sends a draft to SPSC Committee with the successful result of commissioning of single elements of experimental apparatus and request to start installation of phase I in Winter 2011 shutdown, to initiate machine studies in 2012 and to avoid conflicts with ELENA installation during 2013 shutdown.
• Mar. 2012PAX sends to SPSC Committee a draft with the results of spin-filtering studies.
P.Lenisa PAX story 28
The CERN Saga• Oct. 2009 unofficial response from the SPS Committee:… Taking into account the timeline and constraints of the various projects concerned, the SPSC encourages the PAX Collaboration to first perform their spin filtering measurements at COSY, and to report these to the Committee, following which the SPSC will further review the proposal.
• Jan. 2010 Valle’s comment to ERC grant communicationCongratulation for getting approval of an ERC advanced grant… The comments by many of the referees on the risk and schedule issues of your project confort me in the prudent attitude of the SPSC in respect with the necessary related AD modification … Looking forward to the PAX filtering measurements at COSY to proceed further with your review!
• Jan.. 2011Meeting with Heuer• Apr. 2011: SPSC 101 recommendation:The SPSC received a report by the PAX collaboration describing the progress of their program at COSY The SPSC remains concerned by the impact of PAX on the AD antihydrogen programme, the risk factors and manpower requirements for implementing the PAX apparatus at the AD. The Committee considers any installation before the long shutdown to be premature.The Committee is looking forward to the results of the spin filtering measurements.
• Mar. 2012Draft sent to SPSC with final results of August-October 2011 beamtime• Apr. 2012 mail from Vallee.We were pleased to see that you finally succeeded to perform a spin filtering measurement at COSY, showing good control of your apparatus as well as theoretical understanding of spin filtering for protons. However inbetween many positive developments have occured at the AD, leading to an updated program for the coming years which is very constrained on both the scientific and logistic points of view. We consider that PAX is now incompatible with this program.
WASA
e-cooler
ANKE
PAX
Spin-filtering at COSY (2008-2011)
Main purpose:1. Commissioning of the experimental setup for CERN/AD2. Quantitative understanding of the machine parameters
P.Lenisa 29PAX story
ABS
ABS
Breit-Rabi
polarimeter
Breit-Rabi
polarimeter
P.Lenisa 30PAX story
Commissioning (2008-2011):
• 2008-11: Installation and commissioning of the HERMES pol. target
p D2
• 2008-11: Installation and commissioning of the ANKE beam polarimeter
Commissioning (2008-2011):
P.Lenisa 31PAX story
• 2009-10: Installation and commissioning of the low-β section
• 2010-11: Studies of beam-lifetime limitations (: 300 s 8000 s)
P.Lenisa PAX story 32
The CERN Saga: PAX requests• Oct. 2009 PAX request to start phase I of installation not interfering with other experiments.
• Jan. 2010 PAX informs SPSC of acknowledgement of ERC grant.
• Jan.. 2011Meeting with Heuer• Apr. 2011: PAX sends a draft to SPSC Committee with the successful result of commissioning of single elements of experimental apparatus and request to start installation of phase I in Winter 2011 shutdown, to initiate machine studies in 2012 and to avoid conflicts with ELENA installation during 2013 shutdown.
• Mar. 2012PAX sends to SPSC Committee a draft with the results of spin-filtering studies.
P.Lenisa PAX story 33
The CERN Saga• Oct. 2009 unofficial response from the SPS Committee:… Taking into account the timeline and constraints of the various projects concerned, the SPSC encourages the PAX Collaboration to first perform their spin filtering measurements at COSY, and to report these to the Committee, following which the SPSC will further review the proposal.
• Jan. 2010 Valle’s comment to ERC grant communicationCongratulation for getting approval of an ERC advanced grant… The comments by many of the referees on the risk and schedule issues of your project confort me in the prudent attitude of the SPSC in respect with the necessary related AD modification … Looking forward to the PAX filtering measurements at COSY to proceed further with your review!
• Jan.. 2011Meeting with Heuer• Apr. 2011: SPSC 101 recommendation:The SPSC received a report by the PAX collaboration describing the progress of their program at COSY The SPSC remains concerned by the impact of PAX on the AD antihydrogen programme, the risk factors and manpower requirements for implementing the PAX apparatus at the AD. The Committee considers any installation before the long shutdown to be premature.The Committee is looking forward to the results of the spin filtering measurements.
• Mar. 2012Draft sent to SPSC with final results of August-October 2011 beamtime• Apr. 2012 mail from Vallee.We were pleased to see that you finally succeeded to perform a spin filtering measurement at COSY, showing good control of your apparatus as well as theoretical understanding of spin filtering for protons. However inbetween many positive developments have occured at the AD, leading to an updated program for the coming years which is very constrained on both the scientific and logistic points of view. We consider that PAX is now incompatible with this program.
PAX story
p
cluster targ. + STT (beam
polarimetry)
polarized target
COSY ring
Spin-flipper
Spin-filtering at COSY (2011)
P.Lenisa 34
2011: III milestone for PAX
(more about in Dieter’s talk)
P.Lenisa PAX story 35
The CERN Saga: PAX requests• Oct. 2009 PAX request to start phase I of installation not interfering with other experiments.
• Jan. 2010 PAX informs SPSC of acknowledgement of ERC grant.
• Jan.. 2011Meeting with Heuer• Apr. 2011: PAX sends a draft to SPSC Committee with the successful result of commissioning of single elements of experimental apparatus and request to start installation of phase I in Winter 2011 shutdown, to initiate machine studies in 2012 and to avoid conflicts with ELENA installation during 2013 shutdown.
• Mar. 2012PAX sends to SPSC Committee a draft with the results of spin-filtering studies.
P.Lenisa PAX story 36
The CERN Saga• Oct. 2009 unofficial response from the SPS Committee:… Taking into account the timeline and constraints of the various projects concerned, the SPSC encourages the PAX Collaboration to first perform their spin filtering measurements at COSY, and to report these to the Committee, following which the SPSC will further review the proposal.
• Jan. 2010 Valle’s comment to ERC grant communicationCongratulation for getting approval of an ERC advanced grant… The comments by many of the referees on the risk and schedule issues of your project confort me in the prudent attitude of the SPSC in respect with the necessary related AD modification … Looking forward to the PAX filtering measurements at COSY to proceed further with your review!
• Jan.. 2011Meeting with Heuer• Apr. 2011: SPSC 101 recommendation:The SPSC received a report by the PAX collaboration describing the progress of their program at COSY The SPSC remains concerned by the impact of PAX on the AD antihydrogen programme, the risk factors and manpower requirements for implementing the PAX apparatus at the AD. The Committee considers any installation before the long shutdown to be premature.The Committee is looking forward to the results of the spin filtering measurements.
• Mar. 2012Draft sent to SPSC with final results of August-October 2011 beamtime• Apr. 2012 mail from Vallee.We were pleased to see that you finally succeeded to perform a spin filtering measurement at COSY, showing good control of your apparatus as well as theoretical understanding of spin filtering for protons. However inbetween many positive developments have occured at the AD, leading to an updated program for the coming years which is very constrained on both the scientific and logistic points of view. We consider that PAX is now incompatible with this program.
P.Lenisa PAX story 37
Spin-filtering: status in 2012
• No contribution from EM interaction to polarization buildup.
• Only viable solution for “in-situ” polarization is spin-filtering
• Complete understanding of the physics spin-filtering mechanism
• Spin-dependence of proton antiproton interaction still unkown
• New prediction existing
What about the physics case for polarized antiprotons?
38L.L. Pappalardo - QNP2012 – Palaiseau – April 16-20 2012
P
Pxp
Status in 2005: The nucleon collinear structure
P.Lenisa PAX story 38
39L.L. Pappalardo - QNP2012 – Palaiseau – April 16-20 2012
P
Pxp
+ -+ - DF
FF
Status in 2005: Transversity totally unkown!
P.Lenisa PAX story 39
40L.L. Pappalardo - QNP2012 – Palaiseau – April 16-20 2012
Anselmino et al. Phys. Rev. D 75 (2007)
Soffer bound
xh1(x
)d
xh1(x
)u
xh1(x
, k )T
uxh
1(x, k
)T
d
DF
FF
FF
FF+
Tensor charge
1
0 11 )()( xhxhdxq qq
1: Quark-diquark model2: Chiral quark soliton model3: Lattice QCD 4: QCD sum rules
M. Anselmino et al hep-ph:0812.4366
2007 milestone in hadron physics: Transversity first extraction
P.Lenisa PAX story 40
41L.L. Pappalardo - QNP2012 – Palaiseau – April 16-20 2012
DF
FF
2h Semi-Inclusive DIS2011: II independent extraction!
FF
FF+- Survives integration over transverse momentum- Collinear factorization (simple product)- DGLAP evolution
P.Lenisa PAX story 41
42L.L. Pappalardo - QNP2012 – Palaiseau – April 16-20 2012
Phys.Rev.Lett.107:072004,2011
Bacchetta et al., PRL 107 (11) Bacchetta et al., PRL 107 (11)
COMPASS 2010HERMES
2011: II independent extraction!
P.Lenisa PAX story 42
43L.L. Pappalardo - QNP2012 – Palaiseau – April 16-20 2012
Sivers worm-gears
Boer-Mulders
pretzelosity
helicity
transversity
momentum
P
q
Tp
P.Lenisa PAX story 43
2005-2012: A new field has born: The non-collinear structure of the nucleon
P.Lenisa PAX story 44
Physics case for pol.-pbar: status in 2012
• ATT in DY production remains the unique direct way to access h1
• Pbar-p, pbar-d, p-p, p-d collider remains a unique machine to perform the flavour decomposition of transversity
• Interest in Transverse Momentum dependent effect has increased
• PAX physics case should be updated with the novel TMDs
• Interest in proton EMFF has developed:• Different SL experiment addressing two-photon
contribution• Still no individual determination yet of FF in the TL region• Necessity of a complete space-time description
P.Lenisa PAX story 45
PAX between past and future…
• Pol.-pbar remain a missing and unique tool for hadron physics• Antiproton polarization:
• Spin-filtering only viable mechanism • Complete understanding of spin-filtering• Data on spin-dependence of pbar-p interaction needed
• Keep the option open… • … but additional horizon in perspective:
• besides polarization technology for hadron physics… also polarization technology for fundamental physics
• The bridge to the new hera is the new PAX detector:• Longitudinal spin-filtering• Deuteron-breakup• Time Reversal Invariance • … (EDM)
(More about in the talks of Alex, Christian and Yuri…)