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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
January 8, 2011 3
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
January 8, 2011 4
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
January 8, 2011 5
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
January 8, 2011 6
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
6
January 8, 2011 7
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
January 8, 2011 8
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
January 8, 2011 9
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)
9
January 8, 2011 10
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
10
January 8, 2011 11
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
11
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January 8, 2011 23
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
23
January 8, 2011 24
January 8, 2011 25
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January 8, 2011 27
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January 8, 2011 30
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”
30
January 8, 2011 31
Collider experiment LoI• http://www.bnl.gov/npp/docs/pac0610/Crawford_LoI.100524.v1.pdf
31
January 8, 2011 32
Collider experiment LoI
32
January 8, 2011 33
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
January 8, 2011 34
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
34
January 8, 2011 35
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
35
January 8, 2011 36
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
36
January 8, 2011 37
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
37
January 8, 2011 38
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
January 8, 2011 39
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
January 8, 2011 41
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...
January 8, 2011 42
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
47
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Backup slides
January 8, 2011 49
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
50
January 8, 2011 51
RHIC
51
January 8, 2011 52
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
January 8, 2011 53
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?
53
January 8, 2011 54
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
54
January 8, 2011 55
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
55
January 8, 2011 56
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
56
January 8, 2011 57
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
57
January 8, 2011 58
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
January 8, 2011 59
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
59
January 8, 2011 60
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
60
January 8, 2011 61
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)
61
January 8, 2011 62
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
62
January 8, 2011 63
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
63
January 8, 2011 64
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
January 8, 2011 65
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
January 8, 2011 66
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
66
January 8, 2011 67
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
67
January 8, 2011 68
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
68
January 8, 2011 69
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
69
January 8, 2011 70
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
73
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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