19-23 April 2010 DIS 2010 / Florence Neutron Single Target Spin Asymmetries in SIDIS

21 Apr 2010 / DIS10 / Florence E. Cisbani: n SSA @ JLab/Hall A 1

19-23 April 2010

DIS 2010 / Florence

Neutron Single Target Spin Asymmetries in SIDIS

(at JLab HallA)

E. CisbaniINFN Rome and Italian National Institute of Health

on behalf of the 6 GeV Transversity collaboration

http://hallaweb.jlab.org/experiment/transversity/


Outline

• Single Spin Asymmetries in SIDIS

• Transversity Experiment in HallA– Kinematic– Target– Detectors (HRS + BB)– Hadrons Production

• JLab 12 GeV prospective – SBS + SIDIS Experiment– SoLID-Transversity Experiment

Experiment based on the excellent work of several PhD Students:C. Dutta (Kentucky), J. Huang (MIT), A. Kalyan (Kentucky), J. Katich (W&M), X. Qian (Duke), Y. Wang (UIUC), Y. Zhang (Lanzhou U)


Nucleon Structure (at leading twist)

TU

U

L

T

L

quarkn

ucl

eo

n


Method: from SIDIS to SSA to DFFF

Pretzelosity

Evaristo Cisbani

Deltaq - deltaq = k2/M2 * Pretzelosity Pretzelosity difference between elicity and transversity: a measure of the relativistic effects!


Hep

ex-0

802.

2160

Fro

m D

IS20

09F

rom

Pap

pala

rdo

/ Tra

nsve

rsity

200

8

Collins Moments on proton/deuteronCOMPASS/deuteron

proton

Proton:• K- and - with opposite sign, strong flavor

dependence (but K errors significant)!• K+ and + consistent with u dominance• COMPASS compatible with HERMES

Deuteron: consistent with 0, expected asymmetry on neutron as large as on proton

Larger effects at larger x


PLB

673(

2009

)127

COMPASS/deuteron

Sivers Moments on proton/deuteron

PR

L103

(200

9)15

2002

Proton:• K+ twice + conflict with u dominance

expectation• K- and - consistent with 0• COMPASS proton not fully compatible to

HERMESDeuteron: consistent with 0, expected asymmetry on neutron as large as on proton

NEW DATA FROM COMPASS/ProtonSEE H. Fischer talk in this conference

HERMES on p


Extraction of DF and FF from a Global FitTransversity first moment (assume sea = 0)

Collins Fragmentation Function

Ans

elm

ino

et a

l 12/

08

Ans

elm

ino

et a

l 05/

08

Sivers function

e+e- from BELLE (Q2=110 GeV2)

HERMES/p + COMPASS/d (Q2~2.5 GeV2)

Sivers:large s-bar

sea small

Collins: Unfav/Fav FF puzzle(not seen in Unpol FF)


6 GeV CEBAF (< 2013)Max Current: 200 A

Max Energy: 0.8 - 5.9 GeV

Long. Polarization: 85%

JLab Accelerator Facility


Transversity on neutron: Hall A experimental setup• Beam e-:

5.9 GeV, 15 mA

• Neutron Target: High pressure polarized 3He

pol. 65%, 50 mg/cm2 x 40 cmLuminosity: 1036/s/cm2

• Electron Arm (BigBite): E’=0.72.2 GeV,=30°, =64 msr

• Hadron Arm (HRS Left): Ph =2.35 GeV/c ± 5%,=30°, =6 msr, p/K ID

• Kinematic region: Q2 ~ 2.2 GeV2,

x ~ 0.130.45, z ~ 0.5

• Measure Collins, Sivers and Pretzelosity

• Beam e-: 5.9 GeV, 15 mA

• Neutron Target: High pressure polarized 3He

pol. 65%, 50 mg/cm2 x 40 cmLuminosity: 1036/s/cm2

• Electron Arm (BigBite): E’=0.72.2 GeV,=30°, =64 msr

• Hadron Arm (HRS Left): Ph =2.35 GeV/c ± 5%,=30°, =6 msr, p/K ID

• Kinematic region: Q2 ~ 2.2 GeV2,

x ~ 0.130.45, z ~ 0.5

• Measure Collins, Sivers and PretzelosityData Taking:

Nov/08 – Feb/09Data Taking:

Nov/08 – Feb/09

E06-010

e+3He→e’+(K)+X


3He (n) Polarized Target

• Polarized 3He ~ polarized neutron target

• Use 3 COMET lasers (narrow line, high power) for optical pumping of Rb vapor

• Fast spin exchange (via K) by 3He hyperfine

interaction in oven; small part of N2 to quench

soft photon depolarization of Rb

• Polarized 3He diffuses to the target chamber

• Transverse Horizontal (In-plane) and Vertical orientations

• 20 minute spin flip

• NMR and EPR polarimetries

• Superior performances:

– Steady 65% polarization @ 15 uA beam (world record)


Electron Arm (BigBite)


Hadron Arm: HRS-L

1.27


Measured Phase Space

Q2>1, W>2.3, Mm>1.6, 0.3<z<0.7


Preliminary

Hadron Identification• Aerogel Cherenkov Counter

rejection > 98%

• Time of Flight– K/ separation at 4

• RICH proximity focusing detector– K/ separation at 3.8

data from APS2010 / Y. Wang

Ph = 2.33 – 2.47 GeV/c


Projected Stat. on Asymmetries

Work in progress on systematics evaluation

Preliminary results expected to be released within summer/2010 !


JLab at 12 GeV

and

the TMD measurements

prospective in Hall A


CEBAF 12 GeV upgrade

CHL-2CHL-2

Upgrade magnets Upgrade magnets and power and power suppliessupplies

add Hall D (and beam line)

12 GeV CEBAF

(>2014)Max Current: 90 AMax Energy Hall A,B,C: 10.9 GeVMax Energy Hall D: 12 GeVLong. Polarization: 75-85%

310 MUSD

6 GeV CEBAF (< 2013)Max Current: 200 A

Max Energy: 0.8 - 5.9 GeV

Long. Polarization: 85%


Peculiarity of JLab Phase Space

Access unexplored valence region

(high Q2 requires high luminosity)

from TMD-Duke / M. Contalbrigo

Hall A is already running at 1036 and will likely reach

few 1038 (in polarized experiments)


SSA on n in the 11 GeV era in Hall AMeasure Transversity / Sivers / Pretzelosity and more

• SIDIS on and K (conditionally approved, 01/2009) – short term

– G. Cates, E. Cisbani, G.B. Franklin, B. Wojtsekhowski

– Similar layout of the 6GeV experiment at higher luminosity and acceptance

• HRS replaced by a new large acceptance spectrometer (SBS), improved target

– 2D binning on the relevant variables: x, P and z, for both hadrons and Q2 dependence

– High x valence region (with overlap to HERMES, COMPASS, JLab6 data)

– Proposal: http://hallaweb.jlab.org/collab/PAC/PAC34/PR-09-018-sidis.pdf

• SoLID-Transversity experiment (approved, 01/2010) – medium term

– J.-P. Chen, H. Gao, X. Jiang, J.-C. Peng, and X. Qian

– 2 angular coverage

• Use solenoid magnet

– Precision measurement in 4D phase space (x, z, P and Q2)

– Better systematic control due to the 2 geometry

– Extended phase space coverage

– Proposal: http://hallaweb.jlab.org/collab/PAC/PAC35/PR-10-006-SoLID-Transversity.pdf


SIDIS: Experimental Setup

Beam: 50 A, E=8.8 and 11 GeV (80% long. Pol.)Target: 65% polarized 3He GEn(2)/PR-09-016 Luminosity: 1.4×1037 cm-2s-1 , 0.05 sr

e+3He→e’+(K)+X

Event rate: ~104×HERMES60 days of production expected stat. accuracy:

1/10 of proton HERMES

HERMESRICH

Measure the SSA of SIDIS processes n(e,e’p)X and

n(e,e’K)X

BB: e-arm at 30o

= 45 msrGEM TrackerGas CherenkovShower GMn/PR-09-019

SBS:h-arm at 14o

= 50 msrGEM trackerexcellent PID / RICHHadron CALO

PAC34 Conditionally Approved experiment

Evaristo Cisbani

cell: 75 mg of gas = 75 * 6.02 10^20current: 50 uAlumi = 75 * 6.02 * 10^20 * 50 * 10^-6 / (1.6 * 10^-19 = 1.4 10^37In background we use 4 10^37Deatail on calorimenter


SIDIS: A new target

from SBS-IV / G.D. Cates


SIDIS: Hadron PID HERMES RICH

Very stable performance (n/(naerogel-1)= 1%, 9 years)Stored at UVa under safe/controlled conditions(also additional wall of spare Aerogel)

5.5 GeV K+

14.6 GeV e-1.5 GeV -

REAL DATA from NIMA 479 (2002) 511

C4F10 gas


SIDIS: Q2 coverage

Current Transversity Exp. E06-010

Prop. Exp. Ebeam = 8.8 GeV

Prop. Exp. Ebeam = 11.0 GeV

We will investigate the Q2 dependence of the Sivers and Collins functions, with overlap in the region of HERMES; reveal higher twist effects.

Analysis of the Q2 effect will use also the results of 6 GeV E06-010 Transversity experiment


SIDIS: Expected Statistical Accuracy on K

• Superior quality of Kaon data

• Extend at higher x with partial overlap with existing data on proton, deuteron and expected results of HallA Transversity 6 GeV DF from CTEQ5M

FF from DSSRate normalized to HERMES/p+d K production


SoLID: experimental setup

from JLab-PAC35 / X. Qian

E10-006 PAC35 Approved experiment


SoLID: Phase Space

from JLab-PAC35 / X. Qian


SoLID: Projected Data

xfrom JLab-PAC35 / X. Qian


Summary• 6 GeV Transversity Experiment

– Excellent data taking– Almost completed analysis– First results will be released soon (likely before

Summer/2010)

• 12 GeV Prospective– Two complementary experiments proposed on n-

SSA SIDIS in HallA,• different time scale and performance;• both will benefit of JLab luminosity and 3He polarized

targets.


• Backup Slides


Polarized SI-DIS process


SBS for SIDIS


GEn(2) High Lumi Target

• 60% transverse polarization

• Support 60 uA beam current

• Extended target cell (60 cm)• Use proved alkali-hybrid mixture technique for polarization transfer • Improved diagnostics for optimal tuning of the potassium-rubidium ratio• Use line-narrowed high-power diode-laser arrays• Use convection for gas mixing between target and pumping chambers• Better description of the target behavior by the identification of the relaxation rate (X-

term)• Use of metal target cell


Systematics/Physics

• Target FSI relative error: expected <7% following the analysis of Scopetta/Transversity/2008

• Higher Twists:– we will study the Q2 dependence with high

statistics;– terms will be included into the fit whose

stability benefits again of the high statistics– Unpolarized analysis will also be carried on


Systematics/Exp. Apparatus• Random

– dilution factor expected to be small < 1% (S/N = 67/0.3)– Relative error well below 10%

• Vector Meson:– from PHYTIA prediction tuned on HERMES data below 2.5%; lower

at higher x– can be studied at higher z

• Acceptances:– azimuthal angles are well covered even with partial h coverage– X,z,P,Q2 effects suppressed by 2D (at least) binning

• Radiative QED Effects:– Influence x,Q2 and azimuthal angles; PHYTIA can be used to

estimate the correction factor (and systematic error)– According to HERMES we expect a systematic error <5%

• PID:– RICH detector with up to 5% occupancy expect to provide 4

separation at least


Figure of Merit

Two beam energy runs for Q2 dependence studies:


Measure the SSA of SIDIS processes n(e,e’)X and n(e,e’K)X

– Extract Sivers and Collins (and Pretzelosity) asymmetries on and K with high statistics

– Provide 2D binning (at least) on the relevant variables: x, P and z, for

both hadrons

– Provide Q2 dependence

– Explore for the first time the high x valence region (with overlap to HERMES, COMPASS, JLab6 data)

• Understanding of QCD dynamics in the nucleon by the Sivers effect

• Improve knowledge of the nucleon structure in terms of parton distribution functions

• Shed more light on the origin of the nucleon spin

Evaristo Cisbani

Change title in Executive SummaryRemove the "general goals" and write the appaeatus we intend to use, correlation with other experiment and proposal ...


SIDIS 12GeV: What is special

• High Luminosity:– 105 larger than in HERMES– High target polarization (65%)– Fast target polarization switch (120 seconds)– 4 (8) transverse polarization directions

• Use of SBS (and BB):– Large solid angle (50 msr), very good angular and

vertex resolutions– Large momentum coverage (2-7 GeV/c)– Excellent hadron PID

• Reuse equipment from GEp(5) (approved), GEn(2) and GMn (proposals)


Expected Statistical Accuracy on

High x region, with partial overlap with HERMES2D binning in (x,z), (x,P) and (z,P) for and Kand Q2 dependence

5×5 bins (0.15<x<0.65, 0.2<z<0.7) (only one shown)

DF from CTEQ5MFF from DSS

Con

talb

rigo

/SP

IN08


RICH stability in Trans 09

19-23 April 2010 DIS 2010 / Florence Neutron Single Target Spin Asymmetries in SIDIS

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