hep4.nucl.phys.titech.ac.jphep4.nucl.phys.titech.ac.jp/workshop/pacific-spin... · HERA at DESY...

How do the Quarks and Gluons spin in theProton ?

— The View from HERMES —

E.C. Aschenauer

DESY

E.C. Aschenauer Pan Pacific, Tokyo, July 2005 1

The Spin Structure of the Nucleon

Naive Parton Model:∆uv + ∆dv = 1

=⇒ ∆uv =4

3,∆dv =

−1

3

BUT

1988 EMC measured:Σ = 0.123 ± 0.013 ± 0.019

=⇒ Spin Puzzle

1

2=

1

2(∆uv + ∆dv)

F2 from HERA tells:

Gluons are important !

=⇒ sea quarks ∆qs

=⇒ ∆G

1

2=

1

2(∆uv + ∆dv + ∆qs

︸︷︷︸) + ∆G

∆us,∆ds,∆u,∆d,∆s,∆s

Full description of Jq & Jg

needsorbital angular momentum

1

2=

1

2(∆uv + ∆dv + ∆qs)︸︷︷︸

+Lq + (∆G + Lg)

∆Σ


HERA at DESY


HERA at DESY

BeamDirection

Polarimeter

TransversePolarimeter

Spin Rotator

Spin Rotator

pe

Spin RotatorSpin Rotator

Spin Rotator

Spin Rotator

Longitudinal

• HERA-e self-polarizing by emissionof synchrotron radiation−→ Transverse Polarization

• Longitudinal polarization at HERMESvia spin-rotators

• Online measurement of beampolarization with two Comptonback scattering polarimeters

Comparison of rise time curves

0

20

40

60

80

6 6.5 7 7.5 8Time [hours]

Pol

ariz

atio

n [%

]

Transverse Polarimeter

Longitudinal Polarimeter

Beam Polarisation < PB >∼ 55%∆PB/PB = 1.8− 3.4%


The HERMES Detector


The HERMES Detector

1

0

2

−1

−2

m

LUMINOSITY

CHAMBERSDRIFT

FC 1/2

TARGETCELL

DVC

MC 1−3

HODOSCOPE H0

MONITOR

BC 1/2

BC 3/4 TRD

PROP.CHAMBERS

FIELD CLAMPS

PRESHOWER (H2)

STEEL PLATE CALORIMETER

DRIFT CHAMBERS

TRIGGER HODOSCOPE H1

0 1 2 3 4 5 6 7 8 9 10

RICH

SILICON

270 mrad

270 mrad

MUON HODOSCOPEWIDE ANGLE

FRONTMUONHODO

MAGNET

m

IRON WALL

MUON HODOSCOPES

e+

27.5 GeV

140 mrad

170 mrad

170 mrad

140 mrad

Kinematic Range: 0.02 ≤ x ≤ 0.8 at Q2 ≥ 1GeV2 and W ≥ 2GeVΘx ≤ 175 mrad, 40 mrad ≤ Θy ≤ 140 mrad

Reconstruction: δp/p 1.0 - 2.0%, δΘ ≤ 1.0mrad


The HERMES Detector

1

0

2

−1

−2

m

LUMINOSITY

CHAMBERSDRIFT

FC 1/2

TARGETCELL

DVC

MC 1−3

HODOSCOPE H0

MONITOR

BC 1/2

BC 3/4 TRD

PROP.CHAMBERS

FIELD CLAMPS

PRESHOWER (H2)


DRIFT CHAMBERS


0 1 2 3 4 5 6 7 8 9 10

RICH

SILICON

270 mrad

270 mrad


FRONTMUONHODO

MAGNET

m

IRON WALL

MUON HODOSCOPES

e+

27.5 GeV

140 mrad

170 mrad

170 mrad

140 mrad



Internal Gas Target:−→He ,

−→D ,

−→H ,H↑ unpol: H2, D2, He, N2, Ne, Ar, Kr, Xe


The HERMES Detector

1

0

2

−1

−2

m

LUMINOSITY

CHAMBERSDRIFT

FC 1/2

TARGETCELL

DVC

MC 1−3

HODOSCOPE H0

MONITOR

BC 1/2

BC 3/4 TRD

PROP.CHAMBERS

FIELD CLAMPS

PRESHOWER (H2)


DRIFT CHAMBERS


0 1 2 3 4 5 6 7 8 9 10

RICH

SILICON

270 mrad

270 mrad


FRONTMUONHODO

MAGNET

m

IRON WALL

MUON HODOSCOPES

e+

27.5 GeV

140 mrad

170 mrad

170 mrad

140 mrad



Internal Gas Target:−→He ,

−→D ,

−→H ,H↑ unpol: H2, D2, He, N2, Ne, Ar, Kr, Xe

Particle ID: TRD, Preshower, Calorimeter⇒ 1997: Cerenkov 1998 ⇒: RICH + Muon-ID


DIS Kinematics

Inclusive Scattering:

u

*γ

u

(E’, p’)

d

e

q

(E, p)

N

detect scattered lepton

Q2 lab= 4EE′ sin2( θ

2) νlab= E − E′

W 2 lab= M2 + 2Mν − Q2

xlab= Q2

2Mνy

lab= ν

E= p·q

p·k

Q2 determines what can be resolved in theproton

Semi-Inclusive Scattering:

u

*γ

π+

u

(E’, p’)

d

e

q

π

(E, p)

p

KN

detect scattered lepton and

produced hadrons

η =log(Eh

cm−ph||)

2∗(Ehcm+ph

||)

zlab= Eh

ν


Deep Inelastic Scattering

Cross Section: d2σdΩdE2 = α2E′

Q2ELµν(k, q, s)︸︷︷︸

Wµν(P, q, S)︸︷︷︸

leptonic hadronic

Lµν : purely electromagnetic =⇒ calculable in QED

Wµν = −gµνF1

(x,Q2

)+pµpν

νF2

(x,Q2

)

+iεµνλσ qλ

ν

(Sσg1

(x,Q2

)+ 1

ν(p · qSσ − S · qpσ)g2

(x,Q2

))

(for spin 1) −b1

(x,Q2

)rµν + 1

6b2

(x,Q2

)(sµν + tµν + uµν)

+12b3

(x,Q2

)(sµν − uµν) + 1

2b4

(x,Q2

)(sµν − tµν)

F1,F2: Unpolarized Structure Functions=⇒ describe momentum distribution of quarks

g1,g2: Polarized Structure Functions=⇒ describe helicity distribution of quarks


Virtual Photon Asymmetry

σ3/2 ∼ q−(x)

~Sγ + ~SN = 3/2

~SN = − ~Sq

• Virtual photon γ∗ can only couple to quarks of opposite helicity



σ3/2 ∼ q−(x)

~Sγ + ~SN = 3/2

~SN = − ~Sq

σ1/2 ∼ q+(x)

~Sγ + ~SN = 1/2

~SN = ~Sq


• Select q+(x) or q−(x) by changing the orientation of target nucleonspin or helicity of incident lepton beam



σ3/2 ∼ q−(x)

~Sγ + ~SN = 3/2

~SN = − ~Sq

σ1/2 ∼ q+(x)

~Sγ + ~SN = 1/2

~SN = ~Sq



• Different targets =⇒ sensitivity to different quark flavors



σ3/2 ∼ q−(x)

~Sγ + ~SN = 3/2

~SN = − ~Sq

σ1/2 ∼ q+(x)

~Sγ + ~SN = 1/2

~SN = ~Sq



• Different targets =⇒ sensitivity to different quark flavors

Quark Helicity Distributions:

∆qf (x) := q+f (x) − q−f (x)

( f : u,d, s,u,d, s )


F1(x) = 12

∑

i e2i (q

+i (x) + q−i (x)) = 1

2

∑

i e2qi(x)

momentum distribution of quarks

g1(x) = 12

∑

i e2i (q

+i (x) − q−i (x)) = 1

2

∑

i e2∆qi(x)

helicity distribution of quarks

Virtual Photon Asymmetries:

A1 =σ 1

2−σ 3

2

σ 12+σ 3

2

= g1−γ2g2

F1A2 = σTL

σT= γ(g1+g2)

F1

Measurable Asymmetries:

A‖ = σ→⇐−σ

→⇒

σ→⇐+σ

→⇒

A⊥ = σ↑→−σ↑←

σ↑→+σ↑←

A‖ = D(A1 + ηA2) A⊥ = d(A2 + ξA1)

With: D, d,R, ε, γ, ξ, η being kinematic factorsE.C. Aschenauer Pan Pacific, Tokyo, July 2005 8

World data on g1/F1

Proton > Deuterium

0

0.2

0.4

0.6

0.8

1

10-4

10-3

10-2

10-1

1

E 143

E 155 (Q2-averaged by HERMES)

SMC

HERMES

g1p /

F1p

x

<Q2 >/

GeV

2

10-1

1

10

10-4

10-3

10-2

10-1

1

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

10-4

10-3

10-2

10-1

1

HERMES

E 143

E 155 (Q2-averaged by HERMES)

SMC

COMPASS

g1d /

F1d

x

<Q2 >/

GeV

2

10-1

1

10

10-4

10-3

10-2

10-1

1

Data given at measured < Q2 >: 0.02 - 58 GeV2

A|| =1

PbPt

N→⇐L

→⇒

− N→⇒L

→⇐

N→⇐L

→⇒ + N

→⇒L

→⇐

g1

F1

=1

1 + γ2

»

A||

D+ (γ − η)A2

–


World data on xg1(x,Q2)

0

0.02

0.04

0.06

10-4

10-3

10-2

10-1

0

0.02

0.04

10-4

10-3

10-2

10-1

-0.04

-0.02

0

0.02

10-4

10-3

10-2

10-1

xg1

HERMESSMCE155E143

proton

COMPASS

deuteron

E142E154JLAB

neutron (3He)

x

gp1 > gD

1 > g3He1

very precise proton data

most precise deuteron data

0

0.02

0.04

0.06

10-4

10-3

10-2

10-1

0

0.02

0.04

10-4

10-3

10-2

10-1

-0.04

-0.02

0

0.02

10-4

10-3

10-2

10-1

xg1

HERMESSMCE155E143

proton

COMPASS

deuteron

x

neutron (from g1p and g1

d)

gp1 > gD

1 > gn1

very precise proton data

most precise deuteron data

most precise neutron data

gd1 =

1

2(1− 3

2wD)(gp

1 + gn1)

in measured range (0.021-0.9):∫

gp1 = 0.1246 ± 0.0032 ± 0.0074

∫

gd1 = 0.0452 ± 0.0015 ± 0.0017


The structure function b1(x,Q2)

Tensor structure function:

b1 =1

2

∑

q

e2q(2q0 − (q+ + q−))

Adzz =

(σ→⇐ + σ

→⇒) − 2σ0

σ→⇐ + σ

→⇒ + σ0

= −3

2

b1

F1

L µν

Wµν

k

e

k’e’

γ∗ q

p

d

Θ

γ∗

z q q+ 0q


The structure function b1(x,Q2)

• First measurement of Adzz and bd

1

• Adzz 6= 0

• Adzz ∼ 1%

• bd1 > 0 at small x

• in measured range (0.002-0.85):∫

bd1 = (1.05± 0.34± 0.35) · 10−2

• Qualitative agreement withcoherent double-scatteringmodels

-0.02

-0.01

0

0.01

0.02

10-2

10-1

1x

Azzd

-0.05

0

0.05

0.1

0.15

10-2

10-1

1

b1d

10-1

1

10-2

10-1

1x

⟨Q2 ⟩/G

eV2


Semi-inclusive DIS

String Breaking

u_

d_

π0

u_

u_

u_

ρ−

ud0

ud0

π0

π+

π0

−π

u_

u

ud

u

d

u

uu

u

p

incoming leptonscattered lepton

virtual photon

uud

target nucleon


Semi-inclusive DIS

String Breaking

u_

d_

π0

u_

u_

u_

ρ−

ud0

ud0

π0

π+

π0

−π

u_

u

ud

u

d

u

uu

u

p

incoming leptonscattered lepton

virtual photon

uud

target nucleon

Correlation between detected hadron and struck qf=⇒ ’Flavor - Separation’

Inclusive DIS:∆Σ = (∆u + ∆u + ∆d + ∆d + ∆s + ∆s)Semi-inclusive DIS:∆u,∆u,∆d,∆d,∆s,∆s

In LO-QCD:

Ah1(x,Q2) =

σh1/2 − σh

3/2

σh1/2 + σh

3/2

=1 + R(x,Q2)

1 + γ2·∑

f e2f ∆qf (x,Q2)

∫dzDh

f (z,Q2)∑

f e2f qf (x,Q2)

∫dzDh

f (z,Q2)

(∆qf ),qf (Polarized) quark distributionsDh

f (z) fragmentation functions giving the probability that a (struck) quarkof flavor f fragments into a hadron of type h


∆q-Extraction• Rewrite Photon-Nucleon Asymmetry

Ah1(x)

g2=0' C ·∑

q

e2qq(x)

∫dzDh

q (z)∑

q′ e2q′q′(x)

∫dzDh

q′(z)︸︷︷︸

∆q(x)

q(x)

Phq (x, z)

• Purity P hq (x, z): probability hadron h originates from an event with struck

quark f; completely unpolarized quantity

• Extract ∆q by solving:

~A = P ~Q

~A= (A1,p(x),A1,d(x),Aπ±1,p(x),Aπ±

1,d(x),AK±

1,d(x))

~Q= (∆uu

, ∆dd

, ∆uu

, ∆d

d, ∆s

s, ∆s

s)


Measured Hadron Asymmetries

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1

x

-0.1

0

0.1

0.2

0.3

0.4

0.5A1

A1,d

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

A1,dAh+

SMC

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

A1,dAπ+

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

A1,dAK+

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1 0.4

x

-0.1

0

0.1

0.2

0.3

0.4

0.5A1,dAh−

SMC

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1 0.4

x

A1,dAπ−

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1 0.4x

A1,dAK−

0

0.2

0.4

0.6

0.8

10 -1

0.03 0.1

x

A1

A1,p

0

0.2

0.4

0.6

0.8

10 -1

A1,pAh+

SMC

0

0.2

0.4

0.6

0.8

10 -1

A1,pAπ+

0

0.2

0.4

0.6

0.8

10 -1

0.03 0.1 0.4

x

A1,pAh−

SMC

0

0.2

0.4

0.6

0.8

10 -1

0.03 0.1 0.4x

A1,pAπ−

Deuterium

Proton

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1

x

-0.1

0

0.1

0.2

0.3

0.4

0.5A1

A1,d

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

A1,dAh+

SMC

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

A1,dAπ+

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

A1,dAK+

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1 0.4

x

-0.1

0

0.1

0.2

0.3

0.4

0.5A1,dAh−

SMC

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1 0.4

x

A1,dAπ−

-0.1

0

0.1

0.2

0.3

0.4

0.5

10 -1

0.03 0.1 0.4x

A1,dAK−

0

0.2

0.4

0.6

0.8

10 -1

0.03 0.1

x

A1

A1,p

0

0.2

0.4

0.6

0.8

10 -1

A1,pAh+

SMC

0

0.2

0.4

0.6

0.8

10 -1

A1,pAπ+

0

0.2

0.4

0.6

0.8

10 -1

0.03 0.1 0.4

x

A1,pAh−

SMC

0

0.2

0.4

0.6

0.8

10 -1

0.03 0.1 0.4x

A1,pAπ−

Deuterium

Proton

• AK−

1 (x) ≈ 0 !! =⇒ K− = (us)is an all–sea object

• statistics sufficient for5-parameter fit

Q = (∆u

u,∆d

d,∆u

u,∆d

d,∆s

s,∆s

s= 0)


Quark Polarizations0

0.5

10-1

∆u/u

-0.5

0

10-1

∆d/d

-1

0

1

10-1

∆u–/u–

-1

0

1

10-1

∆d–/d–

-1

0

1

10-1

∆s/s

0

5

10

10-1

⟨Q2⟩/GeV2

0.03 0.1 0.6

x

∆qf (x)

qf (x):=

q+f (x)

qf (x)− q−f (x)

qf (x)

• ∆u(x)/u(x) > 0=⇒ polarized parallel to theproton spin

• ∆d(x)/d(x) < 0=⇒ polarized opposite tothe proton spin

• ∆u

u∼ ∆d

d∼ ∆s

s∼ 0


Polarized Quark Densities

0

0.2

10-1

x⋅∆u

-0.2

0

10-1

x⋅∆d

-0.1

0

10-1

GRSV 2000LO val

BB 01 LOx⋅∆u

–

Q2=2.5GeV2

-0.1

0

10-1

x⋅∆d–

-0.1

0

10-1

x⋅∆s

0.03 0.1 0.6

x

∆qf (x) := q+f (x) − q−f (x)

• ∆u(x) and ∆d(x)good agreement with NLO-QCD fit

• ∆u(x),∆d(x) ∼ 0

• No indication for ∆s(x) < 0

• in measured range (0.023-0.6):∫

∆u = -0.002 ± 0.043∫

∆d = -0.054 ± 0.035∫

∆s = +0.028 ± 0.034


SU(2)-Flavor Symmetry Breaking(?)

Unpolarized

0

0.5

1

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Systematic Error

x

d_ -

u_

CTEQ5M CTEQ4M

MRST GRV98

HermesE866

Strong breaking of SU(2)-Flavor Symmetry

Polarized

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

10 -1

0.03 0.1 0.6

x

χQSMmeson cloud

x(∆u–-∆d

–)

Q2 = 2.5 GeV2

No significant breaking ofSU(2)-Flavor Symmetry ∆u ∼ ∆d

More Data needed


How to measure ∆G• ”Indirect” from scaling violation

Remember unpolarized case:HERA F2

0

1

2

3

4

5

1 10 102

103

104

105

F2 em

-log

10(x

)

Q2(GeV2)

ZEUS NLO QCD fit

H1 PDF 2000 fit

H1 94-00

H1 (prel.) 99/00

ZEUS 96/97

BCDMS

E665

NMC

x=6.32E-5 x=0.000102x=0.000161

x=0.000253

x=0.0004x=0.0005

x=0.000632x=0.0008

x=0.0013

x=0.0021

x=0.0032

x=0.005

x=0.008

x=0.013

x=0.021

x=0.032

x=0.05

x=0.08

x=0.13

x=0.18

x=0.25

x=0.4

x=0.65


0

1

2

3

4

5

1 10 102

103

104

105

F2 em

-log

10(x

)

Q2(GeV2)

ZEUS NLO QCD fit

H1 PDF 2000 fit

H1 94-00

H1 (prel.) 99/00

ZEUS 96/97

BCDMS

E665

NMC

x=6.32E-5 x=0.000102x=0.000161

x=0.000253

x=0.0004x=0.0005

x=0.000632x=0.0008

x=0.0013

x=0.0021

x=0.0032

x=0.005

x=0.008

x=0.013

x=0.021

x=0.032

x=0.05

x=0.08

x=0.13

x=0.18

x=0.25

x=0.4

x=0.65

=⇒ big Q2 − xbj lever arm=⇒ very accurate G(x)

0

5

10

15

20

-410 -310 -210 -110 10

5

10

15

20

x

xg

2 = 5 GeV2Q

2 = 20 GeV2Q

2 = 200 GeV2Q

0

5

10

15

20 ZEUS-JETS (prel.) 94-00

H1 PDF 2000

total uncert.

exp. uncert.

total uncert.

H1+ZEUS


0

1

2

3

4

5

1 10 102

103

104

105

F2 em

-log

10(x

)

Q2(GeV2)

ZEUS NLO QCD fit

H1 PDF 2000 fit

H1 94-00

H1 (prel.) 99/00

ZEUS 96/97

BCDMS

E665

NMC

x=6.32E-5 x=0.000102x=0.000161

x=0.000253

x=0.0004x=0.0005

x=0.000632x=0.0008

x=0.0013

x=0.0021

x=0.0032

x=0.005

x=0.008

x=0.013

x=0.021

x=0.032

x=0.05

x=0.08

x=0.13

x=0.18

x=0.25

x=0.4

x=0.65

=⇒ big Q2 − xbj lever arm=⇒ very accurate G(x)

0

5

10

15

20

-410 -310 -210 -110 10

5

10

15

20

x

xg

2 = 5 GeV2Q

2 = 20 GeV2Q

2 = 200 GeV2Q

0

5

10

15

20 ZEUS-JETS (prel.) 94-00

H1 PDF 2000

total uncert.

exp. uncert.

total uncert.

H1+ZEUS

Polarized case:

10-4

10-3

10-2

10-1

1

10

10 2

10 3

10 4

10-1

1 10 102

E143

Q2, GeV2

HERMES

E155

EMC

SMC

• fixed target experiments=⇒ small Q2 − xbj lever arm

• determines only sign of ∆G(x)

-0.4

-0.2

0

0.2

0.4

0.6

0.8

10-3

10-2

10-1

1x


Direct Measurements of ∆G/G

Isolate the photon-gluon fusion process (PGF)

• Select pairs of high-PT oppositely charged hadronsOR

Select single high-PT hadrons

• Reaction: γ∗p → h±1 + h∓2 + X OR γ∗p → h±1 + X

• A|| =N

→⇐h

±1h

∓2

−N→⇒h

±1h

∓2

N→⇐h

±1h

∓2

+ N→⇒h

±1h

∓2

vs. pT(h±1 ,h∓2 ); A|| =N

→⇐h

±1

− N→⇒h

±1

N→⇐h

±1

+ N→⇒h

±1

vs. pT(h±1 )

• low Q2 range (Q2 > 0 GeV2)=⇒ increase statistics=⇒ scale of hard sub-processes p2

T

• require pT (h1,h2) > 0.5 GeV,M(2π) > 1.0 GeV =⇒ removes resonances ρ and φ


Interpretation ?!

Four different processes can contribute:

γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

VMDAVMD = 0 DIS

ADIS ∼ ∆q

q

QCDC

AQCDC ∼ ∆q

q

PGF

APGF ∼ ∆G

G

A‖ ∼4∑

i=1

fi ·Ai ∼ (fQCDCAQCDC + fPGFAPGF + fDISADIS + fXAX)

APGF ≈ 〈a(γg → qq)〉⟨∆G

G

⟩= 〈aPGF〉

︸︷︷︸

⟨∆G

G

⟩

-1

AQCDC ≈ 〈a(γq → qg)〉⟨∆q

q

⟩= 〈aQCDC〉

︸︷︷︸

⟨∆q

q

⟩

+ 12

.. estimate theirrelative contributions fi

using Monte Carlo (PYTHIA-6)=⇒ ∆G/G


Pairs of high-PT Hadrons

pTh2 (GeV/c)

f i (i =

QC

DC

, PG

F, V

MD

)pT

h1>1.5 GeV/c

fPGF

fQCDC

fVMD

0

0.2

0.4

0.6

0.8

1

0.6 0.8 1 1.2 1.4 1.6 1.8-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.6 0.8 1 1.2 1.4 1.6 1.8 2

GSA (<∆G/G> ~ 0.4)GSB (<∆G/G> ~ 0.3)GSC (<∆G/G> ~ -0.1)

pTh2 (GeV/c)

A||(

pTh

1 ,pTh

2 )

pTh1>1.5 GeV/c ∆G/G=-1

∆G/G=0

∆G/G=+1

∆G/G=0.41

Published: within LO pQCD and PYTHIA5 MC model

∆G/G = 0.41 ± 0.18 (stat.) ± 0.03 (exp.syst.)

at 〈xG〉 = 0.17 and 〈p2T 〉 = 2.1 GeV2

6 x more data on polarized Deuterium and new Pythia modified for HERMES

SMC Q2 > 1 GeV2

COMPASS Q2 < 1 GeV2

COMPASS Q2 > 1 GeV2

HERMES Q2 << 0.1 GeV2

HERMES Q2 << 0.1 GeV2 target H/D

HERMES all Q2 GeV2

HERMES Q2 > 0.1 GeV2

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

10-2

10-1

Extraction still Model dependent


Why is a FF extraction important for HERMES

• enter in ∆q, δq and f⊥1T extraction

• test factorization at HERMESenergies

√s ∼ 7GeV

• are the FF from e+e− applicable at ep

and/or⟨Q2

⟩= 2.5GeV

Extract π,K,p multiplicities:

1

NDIS· dNh(z,Q2)

dz=

∑

f

e2f

∫ 1

0dxqf (x,Q2)Dh

f (z,Q2)

∑

f

e2f

∫ 1

0dxqf (x,Q2)


How to extract FF/Multiplicities at HERMESunpolarisedH & D data

experimentalmultiplicitiesin acceptance

unpolarisedH & D data

e+

e−c.s. background

correction


γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC


e+

e−c.s. background

correction


born levelmultiplicities

γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Born level z bin (j)

Exp

erim

enta

l bin

(i)

n(i,j) for all pions

0.04

0.05

0.060.070.080.090.1

0.2

0.3

0.4

0.5

0.60.70.80.9

1

2

0 20 40 60 80 100

Q2 (GeV2/c2)

Du

π+ in

PK

H p

aram

etri

sati

on

z = 0.3

z = 0.7

LONLO


e+

e−c.s. background

correction



Q − Evolution2

acceptance correctionradiative unfolding

γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC


How to extract FF/Multiplicities at HERMES




e+

e−c.s. background

correction


γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC


e+

e−c.s. background

correction



γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Born level z bin (j)

Exp

erim

enta

l bin

(i)


0.04

0.05

0.060.070.080.090.1

0.2

0.3

0.4

0.5

0.60.70.80.9

1

2

0 20 40 60 80 100

Q2 (GeV2/c2)

Du

π+ in

PK

H p

aram

etri

sati

on

z = 0.3

z = 0.7

LONLO


e+

e−c.s. background

correction



Q − Evolution2


γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC


How to extract FF/Multiplicities at HERMES




e+

e−c.s. background

correction


γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC


e+

e−c.s. background

correction



γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Born level z bin (j)

Exp

erim

enta

l bin

(i)


0.04

0.05

0.060.070.080.09

0.1

0.2

0.3

0.4

0.5

0.60.70.80.9

1

2

0 20 40 60 80 100

Q2 (GeV2/c2)

Du

π+ in

PK

H p

aram

etri

sati

on

z = 0.3

z = 0.7

LONLO


e+

e−c.s. background

correction



Q − Evolution2


γ

T T

e+

e+’

’

q

V

h,v

*q

h,

q

+

−

l

−

+

lt

excl. VM correction

PID using RICH

MC


Data - MC Agreement• MC: Lepto in combination with JETSET; PDF: CTEQ-6L

Fragmentation parameters tuned to HERMES multiplicities in acceptance

• Data: Q2 > 1GeV2,W2 > 10GeV2, z > 0.2,2GeV < p(π,K,p)± < 15GeV

PID and background corrections as described before applied

0

0.1

0.2

0.3

0 0.25 0.5 0.75 1 1.25

pt

Mu

ltip

licit

y

pip

0

0.1

0.2

0.3

0 0.25 0.5 0.75 1 1.25

pt

Mu

ltip

licit

y

pim

0

0.02

0.04

0.06

0 0.25 0.5 0.75 1 1.25

pt

Mu

ltip

licit

y

kp

0

0.01

0.02

0.03

0 0.25 0.5 0.75 1 1.25

pt

Mu

ltip

licit

y

km

0

0.05

0.1

0.15

0 0.25 0.5 0.75 1 1.25

pt

Mu

ltip

licit

y

pp

0

0.005

0.01

0.015

0 0.25 0.5 0.75 1 1.25

pt

Mu

ltip

licit

y

pm

Exp.

2004c

2004a

F. all W2

Jetset

0

0.02

0.04

0.06

0.08

0.1

0 1 2 3

rap

Mu

ltip

licit

y

pip

0

0.02

0.04

0.06

0.08

0.1

0 1 2 3

rap

Mu

ltip

licit

y

pim

0

0.01

0.02

0.03

0.04

0 1 2 3

rap

Mu

ltip

licit

y

kp

0

0.005

0.01

0.015

0.02

0 1 2 3

rap

Mu

ltip

licit

y

km

0

0.02

0.04

0.06

0.08

0.1

0 1 2 3

rap

Mu

ltip

licit

y

pp

0

0.002

0.004

0.006

0 1 2 3

rap

Mu

ltip

licit

y

pm

Exp.

2004c

2004a

F. all W2

Jetset

Excellent agreement; also on cross section level (Data/MC < 10%)


Exclusive VM Contamination

• exclusive VM production:totally different process than SIDIS

• estimate contribution from PYTHIA-6:changes: QED-radiation, VMD-model,...

• ratio: Nhexcl.VM(z)/Nh

SIDIS(z)

• large contribution for π at high zcontribution for K moderate vs z

• contribution growing for small xbj forboth π and K

00.5

11.5

22.5

33.5

44.5

0 5 10 15

∆E (GeV)

σ (p

b)

00.20.40.60.8

11.21.41.61.8

2

0 5 10 15

∆E (GeV)

σ Dat

a/σ M

C

0

0.2

0.4

0.6

0.8

1

1.2

0.4 0.6 0.8 1

M(π+π-) (GeV)

σ (p

b)

00.20.40.60.8

11.21.41.61.8

2

0.4 0.6 0.8 1

M(π+π-) (GeV)

σ Dat

a/σ M

C

zN

h V

M(z

)/N

h(z

)

0

0.2

0.4

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.2

0.4

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

π+Target:

ProtonNeutronDeuterium

0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

π-

0

0.025

0.05

0.075

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.025

0.05

0.075

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

K+

0

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

K-

xBjN

h V

M(x

Bj)/

Nh(x

Bj)

0

0.2

0.4

0.6

10 -1 1

0

0.2

0.4

0.6

10-1

1

π+Target:


0.25 < z < 0.350.60 < z < 0.75

0

0.2

0.4

0.6

10-1

1

0

0.2

0.4

0.6

10-1

1

π-

0

0.025

0.05

0.075

0.1

10-1

1

0

0.025

0.05

0.075

0.1

10-1

1

K+

0

0.025

0.05

0.075

0.1

10-1

10

0.025

0.05

0.075

0.1

10-1

1

K-






SIDIS(z)



00.5

11.5

22.5

33.5

44.5

0 5 10 15

∆E (GeV)

σ (p

b)

00.20.40.60.8

11.21.41.61.8

2

0 5 10 15

∆E (GeV)

σ Dat

a/σ M

C

0

0.2

0.4

0.6

0.8

1

1.2

0.4 0.6 0.8 1

M(π+π-) (GeV)

σ (p

b)

00.20.40.60.8

11.21.41.61.8

2

0.4 0.6 0.8 1

M(π+π-) (GeV)

σ Dat

a/σ M

C

zN

h V

M(z

)/N

h(z

)

0

0.2

0.4

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.2

0.4

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

π+Target:


0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

π-

0

0.025

0.05

0.075

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.025

0.05

0.075

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

K+

0

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

K-

xBj

Nh V

M(x

Bj)/

Nh(x

Bj)

0

0.2

0.4

0.6

10 -1 1

0

0.2

0.4

0.6

10-1

1

π+Target:


0.25 < z < 0.350.60 < z < 0.75

0

0.2

0.4

0.6

10-1

1

0

0.2

0.4

0.6

10-1

1

π-

0

0.025

0.05

0.075

0.1

10-1

1

0

0.025

0.05

0.075

0.1

10-1

1

K+

0

0.025

0.05

0.075

0.1

10-1

10

0.025

0.05

0.075

0.1

10-1

1

K-






SIDIS(z)



00.5

11.5

22.5

33.5

44.5

0 5 10 15

∆E (GeV)

σ (p

b)

00.20.40.60.8

11.21.41.61.8

2

0 5 10 15

∆E (GeV)

σ Dat

a/σ M

C

0

0.2

0.4

0.6

0.8

1

1.2

0.4 0.6 0.8 1

M(π+π-) (GeV)

σ (p

b)

00.20.40.60.8

11.21.41.61.8

2

0.4 0.6 0.8 1

M(π+π-) (GeV)

σ Dat

a/σ M

C

zN

h V

M(z

)/N

h(z

)

0

0.2

0.4

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.2

0.4

0.6

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

π+Target:


0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.2

0.4

0.6

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

π-

0

0.025

0.05

0.075

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

0

0.025

0.05

0.075

0.1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

K+

0

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

K-

xBjN

h V

M(x

Bj)/

Nh(x

Bj)

0

0.2

0.4

0.6

10 -1 1

0

0.2

0.4

0.6

10-1

1

π+Target:


0.25 < z < 0.350.60 < z < 0.75

0

0.2

0.4

0.6

10-1

1

0

0.2

0.4

0.6

10-1

1

π-

0

0.025

0.05

0.075

0.1

10-1

1

0

0.025

0.05

0.075

0.1

10-1

1

K+

0

0.025

0.05

0.075

0.1

10-1

10

0.025

0.05

0.075

0.1

10-1

1

K-


π± - Multiplicity vs. z

10-2

10-1

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1z

mu

ltip

licit

y

HERMES Preliminary

π+

excl. VM substractedexcl. VM included

proton target

Q2=2.5 GeV2/c2

10-2

10-1

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1z

mu

ltip

licit

y

HERMES Preliminary

π-


proton target

Q2=2.5 GeV2/c2

• Systematic uncertainty mainly from hadron PID correction

• Q2 > 1GeV2,W2 > 10GeV2


π± - Multiplicity vs. z

10-2

10-1

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1z

mu

ltip

licit

y

HERMES Preliminary

π+

excl. VM substractedexcl. VM includedEMC D(u→π+) FF

proton target

Q2=25.0 GeV2/c2

10-3

10-2

10-1

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1z

mu

ltip

licit

y

HERMES Preliminary

π-

excl. VM substractedexcl. VM includedEMC D(u→π-) FF

proton target

Q2=25.0 GeV2/c2

• Comparison with EMC, Nucl. Phys. B321 (1989) 541

• EMC: Fragmentation Function Dπ±

u


π± - Multiplicity vs. Q2 and xbj

10-1

1

1 10 Q2

(d2 N

π /dz

dQ

2 ) / (

dN

dis

/dQ

2 )

: 0.25 < z < 0.35: 0.35 < z < 0.45

: 0.45 < z < 0.60: 0.60 < z < 0.75

HERMES Preliminary

π+/-


Kretzer FF

proton target

10-1

1

10

10-1

1xbj(d

2 (N

π++N

π-)

/dz

dx)

/ (d

Nd

is/d

x)

: 0.25 < z < 0.35: 0.35 < z < 0.45

: 0.45 < z < 0.60: 0.60 < z < 0.75

HERMES 2000 Preliminary

π

excl. VM substractedexcl. VM includedEMC (charged had.)

proton target

Q2 = 2.5 GeV2/c2

• Reasonable agreement with results using S. Kretzter FF

• very weak xbj dependence


K± - Multiplicity vs. z

10-2

10-1

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1z

mu

ltip

licit

y

HERMES Preliminary

K+


proton target

Q2=2.5 GeV2/c2

10-3

10-2

10-1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1z

mu

ltip

licit

y

HERMES Preliminary

K-


proton target

Q2=2.5 GeV2/c2

• charge separated Kaon multiplicities

• Systematic uncertainty mainly from hadron PID correction

• low K− statistics =⇒ more statistics under way


and Summary

• HERMES continues happily taking data with a transverse polarized p-target

Integrated DIS HERA Run II (polarized)

0

500

1000

1500

2000

2500

3000

x 10 3

0 50 100 150 200 250 300Day of Running

Nu

mb

er o

f p

ol.

DIS

eve

nts

2002/03

2003

2004

2005

• Transversity, Sivers and friends =⇒ G. Schnell• Exclusive reactions =⇒ Lq

DVCS: AUT =⇒ sensitive to GPD H + E =⇒ Ju =⇒ Y. Miyachiexclusive ρ0 / π+: AUT =⇒ sensitive to GPD E / H+ E =⇒ A. Rostomyan

• finalize most of HERA-I analysis

• gd1 ,gp

1 ,gn1 ,b1,∆q

• Extraction of FF very close• new Millennium extraction of ∆q (Purity free)• new ∆s + ∆s extraction using isoscalor method

• the nice description of HERMES data by Monte Carlo will allowa new extraction of ∆G/G

Many more results to come from physics topics not touched in this talk


and Summary

• HERMES continues happily taking data with a transverse polarized p-targetIntegrated DIS HERA Run II (polarized)

0

500

1000

1500

2000

2500

3000

x 10 3

0 50 100 150 200 250 300Day of Running

Nu

mb

er o

f p

ol.

DIS

eve

nts

2002/03

2003

2004

2005




• gd1 ,gp

1 ,gn1 ,b1,∆q





and Summary

• HERMES continues happily taking data with a transverse polarized p-target

Integrated DIS HERA Run II (polarized)

0

500

1000

1500

2000

2500

3000

x 10 3

0 50 100 150 200 250 300Day of Running

Nu

mb

er o

f p

ol.

DIS

eve

nts

2002/03

2003

2004

2005




• gd1 ,gp

1 ,gn1 ,b1,∆q





hep4.nucl.phys.titech.ac.jphep4.nucl.phys.titech.ac.jp/workshop/pacific-spin... · HERA at DESY...

Documents

Transcript of hep4.nucl.phys.titech.ac.jphep4.nucl.phys.titech.ac.jp/workshop/pacific-spin... · HERA at DESY...