January 8, 2011 1

偏極 Drell-Yan実験による核子構造の多次元的理解に向け

て

「核子構造研究の新展開 2011」@KEK2011年 1月 8日 (土 )後藤雄二（理研）

January 8, 2011 2

Outline of this talk• Introduction

– Transverse structure of the proton– Drell-Yan measurement

• Polarized Drell-Yan experiments– COMPASS– GSI– Fermilab– RHIC– J-PARC

• Summary

2

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Introduction• Transverse-spin asymmetry measurement

– Theoretical development to understand the transverse structure of the nucleon

• Sivers effect, Collins effect, higher-twist effect, …• Relation to orbital angular momentum inside the nucleon

FNAL-E704 s = 20 GeV RHIC-STAR s = 200 GeV

3

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Introduction• Transverse-spin asymmetry

– Sivers effect (Sivers function)• Transverse-momentum dependent (TMD) distribution function

– Collins effect (transversity & Collins fragmentation function)

– higher-twist effect– …

• Drell-Yan process– to distinguish Sivers effect– to separate initial-state and final-state interaction with

remnant partons

• Comparison with semi-inclusive DIS results

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Introduction• Transverse structure of the proton

– Transversity distribution function– Correlation between nucleon transverse spin and parton

transverse spin– TMD distribution functions

• Sivers function– Correlation between nucleon transverse spin and parton

transverse momentum (kT)• Boer-Mulders function

– Correlation between parton transverse spin and parton transverse momentum (kT)

Leading-twist transverse momentum dependent (TMD) distribution functions5

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Sivers function• Single-spin asymmetry (SSA)

measurement– < 1% level multi-points

measurements have been done for SSA of DIS process

• Valence quark region: x = 0.005 – 0.3• (more sensitive in lower-x region)

M. Anselmino, et al.EPJA 39, 89 (2009)

Sivers functionu-quark

d-quark

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Polarized Drell-Yan• Many new inputs for remaining proton-spin puzzle

– flavor asymmetry of the sea-quark polarization– transversity distribution– transverse-momentum dependent (TMD) distributions

• Sivers function, Boer-Mulders function, etc.

• “Non-universality” of Sivers function– Sign of Sivers function determined by SSA measurement of

DIS and Drell-Yan processes should be opposite each other

• final-state interaction with remnant partons in DIS process• Initial-state interaction with remnant partons in Drell-Yan process

– Fundamental QCD prediction– One of the next milestones for the field of hadron physics

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Goal of the experiment• Comparison with DIS data

– DIS data• < 1% level multi-points

measurements have already been done for SSA of DIS process

• 0.005 < x < 0.3– Comparable level measurement

needs to be done for SSA of Drell-Yan process for comparison

• Measure not only the sign of the Sivers function but also the shape of the function

• x region– Valence quark region: x ~ 0.2

• Expect to show the largest asymmetry

– … and explore larger x region

M. Anselmino, et al.EPJA 39, 89 (2009)

Sivers functionu-quark

d-quark

8

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Boer-Mulders function• Single transverse-spin asymmetry

– Transversity Boer-Mulders function measurement– Distinguished from Sibers function measurement by different angular

distribution

• Unpolarized measurement– Angular distribution– Violation of the Lam-Tung relation

2 21 31 cos sin 2 cos sin cos 2

4 2

d

d

,

L.Y. Zhu,J.C. Peng, P. Reimer et al.hep-ex/0609005

With Boer-Mulders function h1┴:

ν(π-Wµ+µ-X)~valence h1┴(π)*valence h1

┴(p)

ν(pdµ+µ-X)~valence h1┴(p)*sea h1

┴(p)

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Double-spin asymmetries• Double transverse-spin

asymmetry– transversity– quarkantiquark for p+p

collisions

• Double helicity asymmetry– flavor asymmetry of sea-

quark polarization• SIDIS data from HERMES and

COMPASS preliminary data available

• W data from RHIC will be available in the near future

• Polarized Drell-Yan data will be able to cover higher-x region

2

2

21112

21112

cos1

)2cos(sinˆ

))21()()((

))21()()((

ˆ

21

SSTT

qqqq

qqqq

TTTT

a

xfxfe

xhxhe

aA

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Future polarized Drell-Yan experimentsexperiment particles energy x1 or x2 luminosity

COMPASS + p 160 GeVs = 17.4 GeV

x2 = 0.2 – 0.3 2 × 1033 cm-2s-1

COMPASS(low mass)

+ p 160 GeVs = 17.4 GeV

x2 ~ 0.05 2 × 1033 cm-2s-1

PAX p + pbar colliders = 14 GeV

x1 = 0.1 – 0.9 2 × 1030 cm-2s-1

PANDA(low mass)

pbar + p 15 GeVs = 5.5 GeV

x2 = 0.2 – 0.4 2 × 1032 cm-2s-1

J-PARC p + p 50 GeVs = 10 GeV

x1 = 0.5 – 0.9 1035 cm-2s-1

NICA p + p colliders = 20 GeV

x1 = 0.1 – 0.8 1030 cm-2s-1

RHIC PHENIXMuon

p + p colliders = 500 GeV

x1 = 0.05 – 0.1 2 × 1032 cm-2s-1

RHIC InternalTarget phase-1

p + p 250 GeVs = 22 GeV

x1 = 0.2 – 0.5 2 × 1033 cm-2s-1

RHIC InternalTarget phase-2

p + p 250 GeVs = 22 GeV

x1 = 0.2 – 0.5 3 × 1034 cm-2s-1

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Drell-Yan experiment• Fermilab E966/SeaQuest

– Dimuon spectrometer

– Main injector beam Ebeam = 120 GeV– Higher-x region: x = 0.1 – 0.45– Beam time: 2010 – 2013

Focusing magnetHadron absorberBeam dump

Momentumanalysis

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Polarized Drell-Yan experiments at RHIC• “Transverse-Spin Drell-Yan Physics at RHIC”

– http://spin.riken.bnl.gov/rsc/write-up/dy_final.pdf– Les Bland, et al., May 1, 2007– s = 200 GeV– PHENIX muon arm– STAR FMS (Forward Muon Spectrometer)

• Discussions at PHENIX and STAR underway in their decadal plan discussion with their upgrade plan

• Two new Letter-of-Intent submitted to BNL PAC– Collider experiment dedicated to the polarized Drell-Yan experiment

• “Feasibility Test of Large Rapidity Drell-Yan Production at RHIC”– Fixed-target experiment

• “Measurement of Dimuons from Drell-Yan Process with Polarized Proton Beams and an Internal Target at RHIC”

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Collider experiment LoI• http://www.bnl.gov/npp/docs/pac0610/Crawford_LoI.100524.v1.pdf

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Collider experiment LoI

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Fixed-target experiment LoI• Measurement of Dimuons from Drell-Yan Process with

Polarized Proton Beams and an Internal Target at RHIC– http://www.bnl.gov/npp/docs/pac0610/Goto_rhic-drell-yan.pdf– Academia Sinica (Taiwan): W.C. Chang– ANL (USA): D.F. Geesaman, P.E. Reimer, J. Rubin– UC Riverside (USA): K.N. Barish– UIUC (USA): M. Groose Perdekamp, J.-C. Peng– KEK (Japan): N. Saito, S. Sawada– LANL (USA): M.L. Brooks, X. Jiang, G.L. Kunde, M.J. Leitch, M.X.

Liu, P.L. McGaughey– RIKEN/RBRC (Japan/USA): Y. Fukao, Y. Goto, I. Nakagawa, K.

Okada, R. Seidl, A. Taketani– Seoul National Univ. (Korea): K. Tanida– Stony Brook Univ. (USA): A. Deshpande– Tokyo Tech. (Japan): K. Nakano, T.-A. Shibata– Yamagata Univ. (Japan): N. Doshita, T. Iwata, K. Kondo, Y.

Miyachi33

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Internal target position

IP2 (overplotted on BRAHMS)

DXDOQ1

DX

20 TON

CRANE LIMIT

20 TON

CRANE LIMITCRANE LIMIT

20 TON

CRANE LIMIT

20 TON

POWER PANELS

C

SCALE

0 5' 10'

CRYOGENIC PIPINGCRYOGENIC PIPING

DO Q1 Q2 Q3DO

1EF3

1EF4

2XAV12XAV2

2XEF1

C.O.D.P .

6 each Blocks

3'W X 4'-6 "H X 4'L

3/ 8Ty p

3/ 8Ty p

3/ 8Ty p

3/ 8Ty p

36X80 Man D oorKeyed B B11 &

Card R eader Ac cess

48 X 54 F resh AirInl et G ravity D amper

Q03 Q02 Q01 D0 DXIP

Q03 Q02 Q01 D0 DXIP

36X80 Man D oor

Keyed B B11 &

Card R eader Ac cess

48 X 54 F resh Air

Inl et G ravity D amper

F MAG3.9 mMom.kick2.1 GeV/c

KMAG 2.4 mMom.kick0.55 GeV/c

St.4MuID

14 m18 m

St.1St.2 St.3

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Experimental sensitivities• PYTHIA simulation

– s = 22 GeV (Elab = 250 GeV)– luminosity assumption 10,000 pb-1

• Phase-1 (parasitic operation) 10,000 pb-1

• Phase-2 (dedicated operation) 30,000 pb-1

– 4.5 GeV < M < 8 GeV– acceptance for Drell-Yan dimuon signal is studied

all generateddumuon fromDrell-Yan

accepted byall detectors

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Experimental sensitivities• About 50K events for 10,000pb-1 luminosity

• x-coverage: 0.2 < x < 0.5

Mass(GeV/c2) Total

Rapidity 45 – 50 50 – 60 60 – 80 45 – 80

-0.4 – 0 3.1 K 3.1 K 1.4 K 7.6 K

0 – 0.4 6.2 K 6.1 K 3.0 K 15.3 K

0.4 – 0.8 7.6 K 6.4 K 2.3 K 16.3 K

0.8 – 1.2 4.4 K 2.5 K 0.4 K 7.3 K

x1: x of beam proton (polarized)x2: x of target proton

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Experimental sensitivities• Phase-1 (parasitic operation)

– L = 2×1033 cm-2s-1

– 10,000 pb-1 with 5×106 s ~ 8 weeks, or 3 years (10 weeks×3) of beam time by considering efficiency and live time

• Phase-2 (dedicated operation)– L = 3×1034 cm-2s-1

– 30,000 pb-1 with 106 s ~ 2 weeks, or 8 weeks of beam time by considering efficiency and live time

10,000 pb-1 (phase-1)40,000 pb-1 (phase-1 + phase-2)

Theory calculation:U. D’Alesio and S. Melis, private communication;M. Anselmino, et al., Phys. Rev. D79, 054010 (2009)

Measure not only the sign of the Sivers function but also the shape of the funcion

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J-PARC Drell-Yan proposals• P04: measurement of high-mass dimuon production at the 50-GeV

proton synchrotron– spokespersons: Jen-Chieh Peng (UIUC) and Shinya Sawadas (KEK)– collaboration: Abilene Christian Univ., ANL, Duke Univ., KEK, UIUC, LANL,

Pusan National Univ., RIKEN, Seoul National Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ.

– including polarized physics program, but not discussed– “deferred”

• P24: polarized proton acceleration at J-PARC– contact persons: Yuji Goto (RIKEN) and Hikaru Sato (KEK)– collaboration: ANL, BNL, UIUC, KEK, Kyoto Univ., LANL, RCNP, RIKEN, RBRC,

Rikkyo Univ., TokyoTech, Tokyo Univ. of Science, Yamagata Univ.– polarized Drell-Yan included as a physics case– “no decision”

• Next proposal for the polarized physics program– not yet submitted

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Dimuon experiment at J-PARC (P04)– based on the Fermilab spectrometer for 800 GeV– length to be reduced but the aperture to be increased– two bending magnets with pT kick of 2.5 GeV/c and 0.5 GeV/c– tracking by three stations of MWPC and drift chambers– muon id and tracking

tapered copper beam dump and Cu/C absorbers placed within the first magnet

January 8, 2011 40

Polarized Drell-Yan experiment at J-PARC• Single transverse-spin

asymmetry– Sivers effect measurement

• Experimental condition– higher beam intensity is possible

for unpolarized liquid H2 target, or nuclear target

• 51012 ppp = 2.510122sec in 1pulse (5sec) possible?

– PYTHIA simulation• 75% polarization beam• 120 days, beam on target 51017

(with 50% duty factor)• ~5% liquid H2 target

– 10000 fb-1 luminosity• ~20% nuclear target

– 40000 fb-1 luminosity• mass 4 – 5 GeV/c2

4040

red liquid H2 targetblue nuclear target

analyzingmagnet

127cm51cmpolarizedbeam

4 < M+- < 5 GeVintegrated over qT

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pQCD studies of Drell-Yan cross section• pQCD correction can be controlled at J-PARC energy

NNLO calculationHamberg, van Neerven, Matsuura,Harlander, Kilgore

NLL, NNLL calculationYokoya, et al...

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Polarized proton acceleration (P24)• Polarized beam feasible in discussions with J-PARC and BNL

accelerator physicists• How to keep the polarization given by the polarized proton

source– depolarizing resonance

• imperfection resonance– magnet errors and misalignments

• intrinsic resonance– vertical focusing field

– weaken the resonance• fast tune jump• harmonic orbit correction

– intensify the resonance and flip the spin• rf dipole• snake magnet

• How to monitor the polarization– polarimeters

January 8, 2011 43

Polarized proton acceleration at AGS/RHIC • Proposed scheme for the polarized proton acceleration at J-

PARC is based on the successful experience of accelerating polarized protons to 25 GeV at BNL AGS

BRAHMS& PP2PP

STAR

PHENIX

AGS

LINACBOOSTER

Pol. H- Source

Spin Rotators

200 MeVPolarimeter

AGS InternalPolarimeter

rf Dipole

RHIC pCPolarimeters

Absolute Polarimeter(H jet)

AGS pC PolarimetersCold PartialHelical Siberian Snake

Warm PartialHelical Siberian Snake

PHOBOS

Spin Rotators

Full HelicalSiberian Snakes

Partial Solenoidal Snake

January 8, 2011 44

Polarized proton acceleration at J-PARC

BRAHMS& PP2PP

STAR

PHENIX

AGS

LINACBOOSTER

Pol. H- Source

200 MeVPolarimeter

AGS InternalPolarimeter

rf Dipole

RHIC pCPolarimeters

Absolute Polarimeter(H jet)

AGS pC PolarimetersCold PartialHelical Siberian Snake

Warm PartialHelical Siberian Snake

PHOBOSPol. H- Source

180/400 MeV Polarimeter

rf Dipole

30% PartialHelical Siberian Snakes

pC CNI Polarimeter

Extracted BeamPolarimeter

January 8, 2011 45

Accelerating polarized protons in the MR• AGS 25% superconducting helical snake

helical dipole coil

correction solenoid and dipoles

measured twist angle 2 deg/cmin the middle ~4 deg/cm at ends

January 8, 2011 46

Accelerating polarized protons in the MR• Possible location of partial helical snake magnets in

the MR

First 30% snake Second 30% snake

January 8, 2011 47

Summary• Polarized Drell-Yan measurement

– The simplest process in hadron-hadron reaction– But, not yet done because of technical difficulties so far

• Sivers function measurement in the valence-quark region from the SSA of Drell-Yan process– Test of the QCD prediction “Sivers function in the Drell-Yan

process has an opposite sign to that in the DIS process”– Milestone for the field of hadron physics

• Several proposed (some approved and not-yet-proposed) experiments– COMPASS/GSI/Fermilab/RHIC/J-PARC/…– In this decade

• Measurement not only the sign of the Sivers function, but also the shape of the function feasible

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Backup slides

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RHIC/PHENIX in the future• PHENIX upgrades

– Muon trigger– Silicon VTX– More upgrades discussed in the

decadal plan• RHIC upgrades

– Electron lens & 56 MHz storage RF• EIC (Electron Ion Collider)

– 2020 ?• Spin physics

– 2009-2014(?) W measurement– Helicity structure of the proton

• Quark-spin contribution• Gluon-spin contribution

– Transverse structure of the proton• Orbital angular momentum

– Drell-Yan measurement

49from PHENIX decadal plan

January 8, 2011 50

Introduction• Origin of the proton spin 1/2 - “proton-spin puzzle”

– Polarized DIS experiments– Polarized hadron collision experiments

• Longitudinal-spin asymmetry measurement– Helicity structure of the proton

• Quark-spin contribution• Gluon-spin contribution

– Large restriction for the gluon-spin contribution or gluon helicity distribution

Midrapidity 0 at PHENIXMidrapidity jet at STAR

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RHIC

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Polarized proton acceleration at AGS/RHIC • Successfully operational as a polarized proton collider

BRAHMS& PP2PP

STAR

PHENIX

AGS

LINACBOOSTER

Pol. H- Source

Spin Rotators

200 MeVPolarimeter

AGS InternalPolarimeter

rf Dipole

RHIC pCPolarimeters

Absolute Polarimeter(H jet)

AGS pC PolarimetersCold PartialHelical Siberian Snake

Warm PartialHelical Siberian Snake

PHOBOS

Spin Rotators

Full HelicalSiberian Snakes

Partial Solenoidal Snake

52

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Polarized Drell-Yan experiment• Single transverse-spin asymmetry

– Sivers function measurement– Transversity Boer-Mulders function

• Double transverse-spin asymmetry– Transversity (quark antiquark for p+p collisions)

• Double helicity asymmtry– Flavor asymmetry of quark polarization

• Other physics– Parity violation asymmetry?

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Single transverse-spin asymmetry• Sivers effect

– Correlation between nucleon transverse spin and parton transverse momentum (Sivers distribution function)

– Related to the orbital angular momentum in the proton (and the shape of the proton)

• Multi-dimensional structure of the proton

– Initial-state or final-state interaction with remnant partons

Anselmino, et al., PRD79, 054010 (2009)

J-PARC50-GeVpolarized beams ~ 10 GeV

RHICcolliders = 200 GeV

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DIS Drell-Yan

“toy” QED

QCD

attractive repulsive

Sivers function measurement• Sign of Sivers function determined by single transverse-spin

(SSA) measurement of DIS and Drell-Yan processes– Should be opposite each other

• Initial-state interaction or final-state interaction with remnant partons– Test of TMD factorization– Explanation by Vogelsang and Yuan…

• From “Transverse-Spin Drell-Yan Physics at RHIC,” Les Bland, et al., May 1, 2007

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Sivers function measurement• < 1% level multi-points measurements have already

been done for SSA of DIS process– x = 0.005 – 0.3 (more sensitive in lower-x region)

• comparable level measurement needs to be done for SSA of Drell-Yan process for comparison

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Drell-Yan experiment• The simplest process in hadron-

hadron reactions

– No QCD final state effect• Fermilab E866/NuSea

– Unpolarized Drell-Yan experiment with Ebeam = 800 GeV

– Flavor asymmetry of sea-quark distribution

• x = 0.02 – 0.35 (valence region)

• Fermilab E906/SeaQuest– Similar experiment with main-injector

beam Ebeam = 120 GeV• x = 0.1 – 0.45

DIS Drell-Yan

)(

)(1

2

1~

2 2

2

xu

xdpp

pd

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Drell-Yan experiment• Fermilab E906/SeaQuest

– Dimuon spectrometer

– Main injector beam Ebeam = 120 GeV– Higher-x region: x = 0.1 – 0.45– Beam time: 2010 – 2013

Focusing magnetHadron absorberBeam dump

Momentumanalysis

58

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Drell-Yan experiment• Flavor asymmetry of sea-quark distribution

– Possible origins• meson-cloud model

– virtual meson-baryon state• chiral quark model• instanton model• chiral quark soliton model

– + in the proton as an origin of anti-d quark excess• pseudo-scaler meson should have orbital angular momentum in

the proton…

• Polarized Drell-Yan experiment– Not yet done!– Many new inputs for remaining proton-spin puzzle

• flavor asymmetry of the sea-quark polarization• transversity distribution• transverse-momentum dependent (TMD) distributions

– Sivers function, Boer-Mulders function, etc.

, , npp

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Single transverse-spin asymmetry• Sivers function

– Correlation between nucleon transverse spin and parton transverse momentum (Sivers distribution function)

– Related to the orbital angular momentum in the proton (and the shape of the proton)

• “Non-universality” of Sivers function– Sign of Sivers function determined by SSA measurement of

DIS and Drell-Yan processes should be opposite each other

• final-state interaction with remnant partons in DIS process• Initial-state interaction with remnant partons in Drell-Yan process

– Fundamental QCD prediction– One of the next milestones for the field of hadron physics

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Polarized and unpolarized Drell-Yan experiment • ATT measurement

– h1(x): transversity• quark antiquark in p+p

collisions

• Unpolarized measurement– angular distribution of

unpolarized Drell-Yan– Boer-Mulders function

• violation of the Lam-Tung relation

2

2

21112

21112

cos1

)2cos(sinˆ

))21()()((

))21()()((

ˆ

21

SSTT

qqqq

qqqq

TTTT

a

xfxfe

xhxhe

aA

2 21 31 cos sin 2 cos sin cos 2

4 2

d

d

,

L.Y. Zhu,J.C. Peng, P. Reimer et al.hep-ex/0609005

With Boer-Mulders function h1┴:

ν(π-Wµ+µ-X)~valence h1┴(π)*valence

h1┴(p)

ν(pdµ+µ-X)~valence h1┴(p)*sea h1

┴(p)

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Collider experiment• “Transverse-Spin Drell-Yan

Physics at RHIC”– Les Bland, et al., May 1, 2007– s = 200 GeV– PHENIX muon arm– STAR FMS (Forward Muon

Spectrometer)– Large background from b-

quark– s = 500 GeV may be better…

• Higher luminosity and larger cross section

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Beam time request• Phase-1: parasitic beam time – Option-1

– Beam intensity 2×1011×10MHz = 2×1018/s– Cluster-jet or pellet target 1015atoms/cm2

• 50 times thinner than RHIC CNI carbon target– Luminosity 2×1033/cm2/s– 10,000pb-1 with 5×106s

• 8 weeks, or 3 years (10 weeks×3) with efficiency and live time– Hadronic reaction rate 2×1033×50mb = 108/sec = 100MHz

• 10% beams are used by hadronic reactions in ~6 hours– Beam lifetime

• 2×1011×100bunch / 108 = 2×105s from hadronic reactions• 5×104s = ~15 hours from small-angle scatterings (by D. Trbojevic)• from energy loss?

~6 hours

10% beam used for reaction

collider & internal-targetparasitic run

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Beam time request• Phase-1: parasitic beam time – Option-2 (beam dump mode)

– Beam time at the end of every fill after stopping collider experiments and dumping one beam

– Beam intensity assuming 1011×10MHz = 1018/s– Target with ~1017atoms/cm2 thickness (if available)

• Comparable thickness with RHIC CNI carbon target– Luminosity 1035/cm2/s– Hadronic reaction rate 1035×50mb = 5×109/s = 5GHz

• 20% beams are assumed to be used = 40 pb-1

• In ~ 1,000s depending on how fast the beam dumps?– We request 250 fills to accumulate 10,000 pb-1

• 8 weeks, or 3 years (10 weeks×3) with efficiency and live time?

20% beam used for reaction

collider runinternal-target run 64

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Beam time request• Phase-2: dedicated beam time

– Beam intensity 2×1011×15MHz = 3×1018/s, 1.5 times more number of bunches as assumed at eRHIC

– Pellet or solid target 1016/cm2

• 5 times thinner than RHIC CNI carbon target– Luminosity 3×1034/cm2/s– 30,000pb-1 with 106s

• 2 weeks, or 8 weeks with efficiency and live time– Hadronic reaction rate 3×1034×50mb = 1.5×109/s = 1.5GHz

• 10% beams are used by hadronic reactions in ~30 minutes– Beam lifetime

• 2×1011×150bunch / 1.5×109 = 2×104s from hadronic reactions• 5×103s = ~1.5 hours from small-angle scatterings (by D. Trbojevic)• from energy loss ?

– Even higher luminosity possible, if target with ~1017atoms/cm2

thickness available (beam dump mode)• e.g. 20% beams are used in a shorter period

internal-target run

10% beam used for reaction

~30 mins65

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PYTHIA simulation with IP2 configuration• IP2 configuration shown in the next slide

– detector components from FNAL-E906 apparatus• E906: total z-length ~25 m• IP2: available z-lengh ~14 m

– z-length of FMAG (1st magnet) is shortened• because of limited z-length at IP2

• PYTHIA simulation– just acceptance for Drell-Yan dimuon signal is studied– momentum resolution needs to be studied– background rate needs to be studied

• Beam needs to be restored on axis– after passing through two bending magnets– both beams needs to be restored in parasitic operation

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Collider experiment• Very simple PYTHIA simulation for

PHENIX muon arm– s = 500 GeV– Angle & E cut only

• 1.2 < || < 2.2 (0.22 < || < 0.59)• E > 2, 5, 10 GeV• (no magnetic field, no detector acceptance)

– RHIC-II luminosity assumption 1,000 pb-1

– M = 4.5 8 GeV

rapidity #event- 2.4, - 2.0 5K- 2.0, - 1.6 28K- 1.6, - 1.2 17K- 0.4, 0.0 3K0.0, 0.4 3K1.2, 1.6 18K1.6, 2.0 31K2.0, 2.4 5K

110K events total with 2-GeV cut Red: E > 2 GeV cut Green: E > 5 GeV cut Blue: E > 10 GeV cut

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Collider experiment• Very simple PYTHIA simulation for a dedicated

collider experiment– s = 500 GeV– Angle & E cut only

• || < 2.2• E > 2, 5, 10 GeV• (no magnetic field, no detector acceptance)

– RHIC-II luminosity assumption 1,000 pb-1

– M = 4.5 8 GeV rapidity #event- 2.4, - 2.0 5K- 2.0, - 1.6 32K- 1.6, - 1.2 53K- 1.2, - 0.8 53K- 0.8, - 0.4 60K- 0.4, 0.0 70K0.0, 0.4 68K0.4, 0.8 60K0.8, 1.2 55K1.2, 1.6 54K1.6, 2.0 36K2.0, 2.4 5K

550K events totalwith 2-GeV cut

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Experimental sensitivities• PYTHIA simulation

– s = 22 GeV (Elab = 250 GeV)– luminosity assumption 10,000 pb-1

• 10 times larger luminosity necessary than that of the collider experiments

• because of ~10 times smaller cross section acceptance (in the same mass region)

– 4.5 GeV < M < 8 GeV– acceptance for Drell-Yan dimuon

signal is studied

all generateddumuon fromDrell-Yan

accepted byall detectors

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Fixed-target experiment• PYTHIA simulation with FNAL-E906 geometry

– s = 22 GeV (Elab = 250 GeV)– luminosity assumption 10,000 pb-1

– M = 4.5 8 GeV– Magnetic field and detector location should be tuned to optimize the

acceptance, and fit to available experimental hall

rapidity #event- 0.4, 0.0 1K0.0, 0.4 5K0.4, 0.8 6K0.8, 1.2 3K

16K events total

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all generated dumuonfrom Drell-Yan

accepted by St. 1

passed through St. 1passed through St. 2

passed through St. 3

accepted by all detectors

Drell-Yan dimuon rapidity

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Drell-Yan x1 vs x2 (accepted events)

• x1: x of beam proton (polarized)

• x2: x of target proton

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Drell-Yan E1 vs E2 (accepted events)

• E1, E2: energy of dimuons– energy cut shown at 5 – 10 GeV

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Comparison• x1 & x2 coverage

– PHENIX muon arm• Single arm: x1 = 0.05 – 0.1 (x2 = 0.001 – 0.002)

– Very sensitive x-region of SIDIS data• Back-to-back: small x1 & x2

– Fixed-target experiment• x1 = 0.25 – 0.4 (x2 = 0.1 – 0.2)

– Can explore higher-x region with better sensitivity

PHENIX muon arm Fixed-target experiment

x1

x2

x1

x2

rapidity rapidity74

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Issues for the fixed-target experiment• Requirement for target thickness

– In phase-1 (parasitic operation), 1015 /cm2 thickness is necessary to achieve L = 21033 cm-2s-1

• Pellet target (~1015 /cm2) or cluster-jet target (up to 81014/cm2 ?) is necessary

• If it is not achieved, the internal-target experiment would not be competitive against collider experiments

• In collider experiments, L = 2(or 3)1032 is expected and cross section ( acceptance) is >10 times larger

– In phase-2 (dedicated operation), 10-times larger thickness, 1016 /cm2 is expected

• Requirement for accelerator– Compensation of dipole magnets in the experimental apparatus

(in two colliding-beam operation)– Size of the experimental site and possible target-position (with

proper beam operation)– Reaction rate (peak rate) and beam lifetime– Radiation issues

• Beam loss/dump requirement75

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To-do list• Low-mass region study

– 2 – 2.5 GeV– Larger yield– covering lower x region

• 0.1 < x < 0.45– With lower magnetic field?– Charm background < 20% (PYTHIA)

• Geometry optimization– Opposite polarity of two magnets

• May be better for restoring beams on axis– Aperture study of the magnets

• For inventory check of BNL magnets

• GEANT simulation– Background rate study

• From the beam pipe?• Effect for the DX magnet?• Peak rate?

• Internal target study

2<M<2.5 GeV(1,000 pb-1)

4.5<M<8 GeV(10,000 pb-1)

2<M<2.5 GeV

Drell-Yan

Charm

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Internal target• Cluster-jet target

– H2, D2, N2, CH4, Ne, Ar, Kr, Xe, …– 1014 – 1015 atoms/cm2

– Prototype of the PANDA target is operational at the Univ. of Muenster with a thickness of 8×1014 atoms/cm2

• Pellet target– H2, D2, N2, Ne, Ar, Kr, Xe, …– 1015 – 1016 atoms/cm2

– First-generation target was developed in Uppsala and is in use with the WASA@COSY experiment

– Prototype of the PANDA target is available at Juelich which has been developed in collaboration with Moscow groups (ITEP and MPEI)

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Experimental sensitivities

accepted4.5 - 8 GeV/c2

4.5 - 5 GeV/c2

5 - 6 GeV/c2

6 - 8 GeV/c2

rapidity

x1

xF

pT

all generated dumuonfrom Drell-Yan

passed through FMAGpassed through St. 1passed through St. 2passed through St. 3accepted by all detectors

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Collider vs fixed-target• x1 & x2 coverage

– Collider experiment with PHENIX muon arm (simple PYTHIA simulation)• s = 500 GeV• Angle & E cut only

– 1.2 < || < 2.2 (0.22 < || < 0.59), E > 2, 5, 10 GeV– (no magnetic field, no detector acceptance)

• luminosity assumption 1,000 pb-1

• M = 4.5 8 GeV• Single arm: x1 = 0.05 – 0.1 (x2 = 0.001 – 0.002)

– Very sensitive x-region of SIDIS data– Fixed-target experiment

• x1 = 0.2 – 0.5 (x2 = 0.1 – 0.2)– Can explore higher-x region with better sensitivity

PHENIX muon arm (angle & E cut only)

x1

x2 x2

x1

Fixed-target experiment

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Charm/bottom background• In collider energies, there is non-negligible

background from open beauty production• In fixed-target energies, background from charm &

bottom production is negligible

charm

bottom

Drell-Yan

PHENIX muon arms = 200 GeV

FNAL-E866Elab = 800 GeV

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Charm/bottom background• In collider energies, there is non-negligible

background from open beauty production• In fixed-target energies, background from

charm & bottom production is negligible at 4.5 - 8 GeV mass region

• At 2 - 2.5 GeV low-mass region– Larger yield– covering lower x region

• 0.1 < x < 0.45– Charm background < 20% (PYTHIA)

charm

bottom

Drell-Yan

PHENIX muon arms = 200 GeV

2<M<2.5 GeV(1,000 pb-1)

4.5<M<8 GeV(10,000 pb-1)

2<M<2.5 GeV

Drell-Yan

Charm

81