# Presentation: 593682

## Spin-physics with Polarized Antiprotons

- Forschungszentrum Jülich

**http://www.fz-juelich.de/ikp/pax**

## PAX Collaboration

*Department of Subatomic and Radiation Physics, University of Gent, ****Belgium***
*University of Science & Technology of China, Beijing, P.R.**** China***
*Department of Physics, Beijing, P.R. ****China***
***Palaiseau, Ecole Polytechnique Centre de Physique Theorique, ******France***
*High Energy Physics Institute, Tbilisi State University, Tbilisi, ****Georgia***
***Nuclear Physics Department, Tbilisi State University******, Georgia***
*Forschungszentrum Jülich, Institut für Kernphysik Jülich, ****Germany***
*Institut für Theoretische Physik II, Ruhr Universität Bochum**, ****Germany***
*Helmholtz-Institut für Strahlen- und Kernphysik, **Bonn, ****Germany***
*Physikalisches Institut, Universität Erlangen-Nürnberg**, ****Germany***
***Langenbernsodorf, UGS, Gelinde Schulteis and Partner GbR,***** ****Germany**
***Department of Mathematics, University of Dublin,Dublin,****** Ireland***
***Università del Piemonte Orientale and INFN,****** ******Alessandria,*** ***Italy***
***Dipartimento di Fisica dell’Università and INFN, Cagliari,****** Italy***
***Università dell’Insubria and INFN,****** ******Como,*** ***Italy***
*Instituto Nationale di Fisica Nuclelare, **Ferrara, ****Italy***

- Spokespersons:
- 	Paolo Lenisa		lenisa@mail.desy.de
- 	Frank Rathmann 		f.rathmann@fz-juelich.de

## PAX Collaboration

*Instituto Nationale di Fisica Nucleare, **Frascati, ****Italy***
***Andrej Sultan Institute for Nuclear Studies, Dep. of Nuclear Reactions, Warsaw,****** Poland***
*Petersburg Nuclear Physics Institute, Gatchina, ****Russia**** *
*Institute for Theoretical and Experimental Physics, Moscow, ****Russia***
*Lebedev Physical Institute, Moscow, ****Russia***
***Physics Department, Moscow Engineering Physics Institute, Moscow,****** Russia***
***Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna******, Russia***
*Laboratory of Particle Physics, Joint Institute for Nuclear Research, Dubna, ****Russia***
*Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Dubna, ****Russia***
***Budker Institute of Nuclear Physics, Novosibirsk,****** Russia***
*High Energy Physics Institute, Protvino, ****Russia***
***Institute of Experimental Physics, Slovak Academy of Science, Kosice****** Slovakia***
*Department of Radiation Sciences, Nuclear Physics Division, Uppsala University, Uppsala, ****Sweden***
***Collider Accelerator Department, Brookhaven National Laboratory, Broohhaven****** USA***
***RIKEN BNL Research Center Brookhaven National Laboratory, Brookhaven******, USA***
***University of Wisconsin, Madison,****** USA***
***Department of Physics, University of Virginia,****** USA***

**~180 scientists**
**35 Institutions (15 EU, 20  Non-EU)**

## The PAX proposal

- Jan. 04 	LOI submitted
- 15.06.04	QCD PAC meeting at GSI
- 18-19.08.04	Workshop on polarized antiprotons at GSI
- 15.09.04 	F. Rathmann et al., *A Method to polarize stored *
*	**	**	**antiprotons to a high degree* (PRL 94, 014801 (2005))
- 15.01.05 	Technical Report submitted
- 14-16.03.05	QCD-PAC meeting at GSI
- 			**Polarization enters in the core of FAIR**

## Outline

- WHY? 			Physics Case
- HOW? 			Polarized Antiprotons
- WHAT?			Staging
- 					Detector and Signal Estimate
- WHEN?		 	Timeline

## Physic Topics

- Transversity
- Electromagnetic Form Factors
- Hard Scattering Effects
- SSA in DY, origin of Sivers function
- Soft Scattering
- Low-t Physics
- Total Cross Section
- _p_p interaction

**Physics **** Polarization **** ****Staging   Signals  Timeline**

## Central PAX Physics Case: 
Transversity distribution of the nucleon in Drell-Yan:	 FAIR as successor of DIS physics
last leading-twist missing piece of the QCD description of the partonic structure of the nucleon
observation of h1q (x,Q2) of the proton for valence quarks (ATT in Drell-Yan >0.2) 
transversely polarized proton beam or target ()
transversely polarized antiproton beam ()

- Central PAX Physics Case:
- Transversity distribution of the nucleon in Drell-Yan:	 FAIR as successor of DIS physics
- last leading-twist missing piece of the QCD description of the partonic structure of the nucleon
**observation of h****1****q**** ****(x,Q****2****) of the proton for valence quarks **(ATT in Drell-Yan >0.2)
**transversely polarized proton beam or target (********)**
**transversely polarized antiproton beam**** (********)**

- HESR

- QCD Physics at FAIR (CDR):
- unpolarized Antiprotons in HESR

- PAX  Polarized Antiprotons

**Physics **** Polarization **** ****Staging   Signals  Timeline**

## Leading Twist Distribution Functions 

- Leading Twist Distribution Functions

**+**

- f1(x)

- h1(x)

- u = 1/2(uR + uL)
- u = 1/2(uR - uL)

- No probabilistic interpretation in the helicity base (off diagonal)

- Probabilistic interpretation
- in helicity base:

- q(x) spin averaged
**(well known)**

- q(x) helicity diff.
**(known)**

- q(x) helicity flip
**(unknown)**

**-**

- g1(x)

- Transversity
- base

## Transversity

**Physics **** Polarization **** ****Staging   Signals  Timeline**

## Transversity in Drell-Yan processes

**Physics **** Polarization **** ****Staging   Signals  Timeline**

## Proton Electromagnetic Formfactors 

- Measurement of relative phases of magnetic and electric FF in the time-like region
- Possible only via SSA in the annihilation _p_p → e+e-
- Double-spin asymmetry
- independent GE-Gm separation
- test of Rosenbluth separation in the time-like region

- S. Brodsky et al.,
- Phys. Rev. D69 (2004)

**Physics **** Polarization **** ****Staging   Signals  Timeline**

## Study onset of Perturbative QCD

- p (GeV/c)

- Pure Meson Land
-  Meson exchange
-  ∆ excitation
-  NN potential models

- Transition Region
- Uncharted Territory
- Huge Spin-Effects in pp elastic scattering
**large ****t****: non-and perturbative QCD**

- High Energy
-  small t: Reggeon Exchange
-  large t: perturbative QCD

**Physics **** Polarization **** ****Staging   Signals  Timeline**

## pp Elastic Scattering from ZGS/AGS

- Spin-dependence at large-P (90°cm):
**Hard scattering takes place only with spins ********.**

- Similar studies in _p_p elastic scattering

**Physics **** Polarization **** ****Staging   Signals  Timeline**

- A. Krisch Sci. Am. 257 (1987)
- “The results challenge the prevailing theory that describes the proton’s structure and forces”

**Notes:**
t=-2Pcm2(1-cos(cm))

## Outline

- WHY? 			Physics Case
- HOW? 			Polarized Antiprotons
- WHAT?			Staging
- 					Detector and Signal Estimate
- WHEN? 			Timeline

## Principle of Spin Filter Method

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Principle of Spin Filter Method

**Polarized H target**

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## 1992 Filter Test at TSR with protons

- Experimental Setup

- Results

- F. Rathmann. et al.,
- PRL 71, 1379 (1993)

**T=23 MeV**

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

| Expectation |  |
| --- | --- |
| Target | Beam |
|  |  |
|  |  |

- For low energy pp scattering:
- 1<0  tot+<tot-

## Experimental Setup at TSR (1992)

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Puzzle from FILTEX Test

**Observed** polarization build-up: dP/dt = ± (**1.24 ± 0.06**) x 10-2 h-1

**Expected** build-up: P(t)=tanh(t/τpol),
-  1/τpol=σ1Qdtf**=2.4x10****-2 ****h****-1**
****** ****about factor 2 larger!**

- σ1 = 122 mb (pp phase shifts)
- Q = 0.83 ± 0.03
- dt = (5.6 ± 0.3) x 1013cm-2
- f = 1.177 MHz

**Three distinct effects:**
**Selective removal through scattering beyond ****Ψ****acc****=4.4 mrad**** ****	**		**σ****R********=83 mb**
**Small angle scattering of target protons into ring acceptance** 			**σ****S********=52 mb**
**Spin transfer from polarized electrons of the target atoms to the stored protons**** **
**	****	****σ****EM********=70 mb (-)**

- Horowitz & Meyer, PRL 72, 3981 (1994)
- H.O. Meyer, PRE 50, 1485 (1994)

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Beam lifetimes in the APR

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Polarization Buildup: Optimum Buildup Time

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Beam Polarization(Electromagnetic Interaction)

- Buildup in HESR (800 MeV)

- Beam Polarization(Electromagnetic Interaction)

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Beam Polarization (Hadronic Interaction)

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

**Experimental Tests required:**
**EM effect needs protons only (COSY)**
**Final Design of APR: Filter test with **_**p**_** at AD (CERN)**

## Polarized Internal Target

| point-like | 5-10 mm | free jet | low density | 1012 cm-2 |
| --- | --- | --- | --- | --- |
| extended | 200-500 mm | storage cell | high density | 1014 cm-2 |

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## Performance of Polarized Internal Targets

- Transverse Field (B=297 mT)

- HERMES: Stored Positrons

- PINTEX: Stored Protons

**Targets work very reliably (months of stable operation)**

**Physics **** Polarization**** **** ****Staging   Signals  Timeline**

## APR

- e-Cooler

**APR**

**ABS**

**Polarizer Target**

- Internal
- Experiment

- Siberian Snake

- Injection

- 150 m

- F. Rathmann et al.,
- PRL 94, 014801 (2005)

- Extraction

- e-Cooler

**Small Beam Waist at Target** 	**β****=0.2 m**
**High Flux ABS**		  	**q=1.5****·10****17**** s****-1**
****** ****Dense Target**		T=100 K, longitudinal Q (300 mT)
- 	            beam tube	db=ψacc·β·2**d****t****=d****t****(****ψ****acc****)**, lb=40 cm (**=****2·****β**)
-                       feeding tube 	df=1 cm, lf=15 cm

- Very Large Acceptance APR

## Outline

- WHY? 			Physics Case
- HOW? 			Polarized Antiprotons
- WHAT?			Staging
- 					Detector and signal estimate
- WHEN?	 		Timeline

## Facilty for Antiproton and Ion Research

-  (GSI, Darmstadt, Germany)

-  Proton linac (injector)
-  2 synchrotons (30 GeV p)
-  A number of storage rings
-  Parallel beams operation

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

##  The FAIR project at GSI

**FLAIR:**
**(Facility for very Low energy Anti-protons and fully stripped Ions)**

**SIS100/300**

**HESR: High Energy Storage Ring:**
**PANDA and PAX**

**NESR**

**CR-Complex**

-  The FAIR project at GSI

- 50 MeV Proton Linac

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

## The Antiproton Facility

- HESR

**Antiproton ****Production Target**

**HESR (High Energy Storage Ring)**
**Length 442 m**
**B****ρ**** = 50 Tm**
**N = 5 x 10****10**** antiprotons**
**High luminosity mode**
**Luminosity = 2 x 10****32**** cm****-2****s****-1**
**Δ****p/p ~ 10****-4****  (stochastic-cooling**)
**High resolution mode**
**Δ****p/p ~ 10****-5****  (8 MV HE e-cooling)**
**Luminosity = 10****31**** cm****-2****s****-1**

**Antiproton production similar to CERN**** **
**Production rate**** ****10****7****/sec at ~30 GeV/c**
**T = 1.5 - 15 GeV/c***** *****(22 GeV)**

**Gas Target and Pellet Target: **
***cooling power determines thickness***

- Super
- FRS

- NESR

- CR

**Beam Cooling:**** **
**e****-**** and/or stochastic**
**2MV prototype e-cooling at COSY**

**SIS100/300**

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

## PAX Accelerator Setup

- Antiproton Polarizer Ring (APR)
**+**
- Cooler Storage Ring (CSR, COSY-like): 3.5 GeV/c
**+**
- HESR: 15 GeV/c
****** ****Asymmetric Double-Polarized Antiproton-Proton Collider**

- HESR

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

## Phase I: PAX at CSR

**Physics:****	****Electromagnetic Form Factors**
**	****	**_**p**_**p elastic scattering**

**Experiment:****	**** polarized/unpolarized **_**p**_** on polarized target**

**Independent of HESR experiments**

- HESR

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

## Phase II: PAX at CSR

**EXPERIMENT: **Asymmetric Collider:
- 	**Polarized Antiprotons in HESR (15 GeV/c)**
- 	**Polarized Protons in CSR (3.5 GeV/c)**

**Physics: ****Transversity**

**Second IP with minor interference with PANDA**

- HESR

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

## HESR Injection cycle

- Factor of 10 loss
- (2 lifetimes)

- APR space charge limit

- CSR space charge limit

- protons

- 10 bunches
- of 1010 pbar

**Physics  Polarization **** ****Staging****   Signals**** **** Timeline**

## Outline

- WHY? 			Physics Case
- HOW? 			Polarized Antiprotons
- WHAT?			Staging
- 					Detector and Signal Estimate
- WHEN?	 		Timeline

## Transversity in Drell-Yan processes

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## ATT for PAX Kinematic Conditions

**s~200 GeV****2**** ideal:**
**Large range in x****F**** **
**Large asymmetry,**** (h****1****u****/u)****2**** ~ ****A****TT**

**RHIC**: **τ****=x****1****x****2****=M****2****/s~10****-3**** **
**→**** ****Exploration of ****sea quark**** content:**** **ATT small (~ 1 %)
**PAX**: **M****2****~10 GeV****2****, s~200 GeV****2**
**τ****=x****1****x****2****=M****2****/s~0.05**
**→** **Exploration of** **valence quarks ****h****1****q****(x,Q****2****) large**

- ATT/aTT > 0.2 Models predict |h1u|>>|h1d|

- xF=x1-x2

- Anselmino et al., **PLB 594,97 (2004)**
- Efremov et al., **EPJ C35, 207 (2004)**

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## Kinematics and cross section

- M2 = s x1x2
- xF=2QL/√s = x1-x2

- Estimated luminosities:
**Fixed target: ****	****2.7x10****31**** cm****-2****s****-1**
**Collider:****	****1-2 x 10****30**** cm****-2****s****-1**

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## PAX conceptional Detector Design

**Designed for Collider but compatible with fixed target**

- Cerenkov

**(200 ********m)**

**(20 ********m)**

**GEANT simulation**

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## Estimated signal for h1 (Phase II)

- Estimated signal for h1 (Phase II)

**1 year of data taking**

**Collider:**
**L=2x10****30**** cm****-2****s****-1**

**Fixed target:**
**L=2.7x10****31**** cm****-2****s****-1**

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## Estimated signal for EMFF (Phase I)

| Beam
(MeV/c) | 
 (GeV2) | e+e-
(nbarn)* | L
(cm-2s-1) | Days
DS | Days
SS |
| --- | --- | --- | --- | --- | --- |
| 549 | 3.76 | 7.3 | 7.8x1030 | 2.9 | 0.3 |
| 900 | 4.18 | 3.7 | 1.1x1031 | 4.7 | 0.5 |
| 3600 | 8.75 | 0.044 | 1.5x1031 | 132 | 13 |

- Npbar = 1x1011
- f=LCSR/c
- dt=1x1014cm-2
- Q=0.8 (p pol)
- P=0.3 (pbar pol)
- =0.5

- Estimated signal for EMFF (Phase I)

**PS170 ****and E835**

**PAX could run down to 200 MeV/c with double polarization**

**Running days to get ********O = 0.05**

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## Estimated Signal for pp elastic (Phase I)

- BNL E838

- Estimated Signal for _p_p elastic (Phase I)

**Cross section estimation for p=3.6 GeV/c, ********=120****°**

**Event rate (********t=0.1 GeV****2****):**

**2 hours to get**

- N10

**Physics  Polarization **** ****Staging   ****Signals **** Timeline**

## Outline

- WHY? 			Physics Case
- HOW? 			Polarized Antiprotons
- WHAT?			Staging
- 					Detector and signal estimate
- WHEN?		 	Timeline

##  Timeline

**	****Polarizer design and construction.**
**	****Physics: polarizing cross-section measurements ****	****(COSY & CERN).**

**Phase I: 2013-2017**
**	****APR+CSR @ GSI**
**	****Physics: EMFF, p-pbar elastic with fixed target.**

**Phase II: 2018 - ...**
**	****HESR+CSR asymmetric collider**
**	****Physics: h****1**** ****	**

-  Timeline

**Physics**** **** Polarization **** ****Staging   Signals  ****Timeline**

## Conclusions

**Challenging opportunities accessible with polarized **_**p**_**’s**
- Unique access to a wealth of new fundamental physics observables
- Central physics issue: h1q (x,Q2) of the proton in DY processes
- Other issues:
- Electromagnetic Formfactors
- Polarization effects in Hard and Soft Scattering processes
- differential cross sections, analyzing powers, spin correlation param.
**Staged approach**
- Filter Tests Experiments with protons (COSY) and antiprotons (CERN)
**Projections for double polarization experiments:**
- Pbeam > 0.20
- L> 1.6 ·1030 cm-2s-1 (Collider)
- L 2.7 ·1031 cm-2s-1 (fixed target)
**Detector concept:**
- Large acceptance detector with a toroidal magnet