Alessandro Bravar

S U M M A R YS U M M A R Y

XIXIthth Advanced Research Workshop Advanced Research Workshop

Spin-05, Dubna, Spin-05, Dubna,

September 27-October 1, 2005September 27-October 1, 2005

SPIN at High Energies: Workshops in SPIN at High Energies: Workshops in DubnaDubna

First – 1981 under the Chair of Lev Iosifovich Lapidus (1927-1986), prominent scientist who laid down the fundamentals of high energy spin physics Biannual workshops (in odd

years, between Spin Symposia) in Protvino and (1997, 2001, 2003) Dubna

SOME DUE WORDS …SOME DUE WORDS …Workshop supported by- Russian Foundation for Basic Research- International Committee of Spin Physics Symposia - JINR

Many thanks to Anatoli Efremov, and the organizing committeefor organizing this very interesting and stimulating meetingand also for the very good weather

85 talks: experiments and new results, future, theory,spin technology

This workshopThis workshopdedicated to the memory ofdedicated to the memory ofProf. Mikhail Petrovich Rekalo (1938-2004)Prof. Mikhail Petrovich Rekalo (1938-2004)

Prominent scientist who made important contributions to the spin physics (talk by I.M. Sitnik)

In particular – early studies of T-odd spin asymmetries : currently popular subject to be much discussed at this Workshop

GENERAL OUTLINE …GENERAL OUTLINE …

proton spininclusive, semi-inclusive, gluon polarization, transversity

transverse spin -> SSATMD, Sivers, Collins, Cahn, … effectsSivers in Drell-Yan ?

Generalized Parton DistributionsDVCS, DVMP, … -> Lq

elastic scatteringHigh Energy, Medium and Lowbinary reactions

spin technologyAcceleartion, sources, targets, polarimeters, …

future

Proton Spin “puzzle”Proton Spin “puzzle”

The Spin of the nucleon made of:

|p = ½ = ½ + G + Lq + Lg

= u + d + s Spin of Quarks

G Spin of Gluons

Lq, Lg Orbital angular momentum

Naïve expectations: quarks carry all the nucleon spin = 1+ relativistic effects = 0.6, Lq = 0.4

but … EMC (’89): = 0.12 ± 0.09 ± 0.014 s = 0.19 ± 0.03 ± 0.05 consisten with 0 “Spin crisis”

s < 0 generated by axial anomaly large G > 0 curiosity: existence of proton spin first deduce from specific heats of H2

q(x)

q(x)

Tq(x)

momentum distribution

helicity distribution

transversity distribution

Parton Distribution Parton Distribution FunctionsFunctions3 distribution functions are necessary to describe

the structure of the nucleon at LO:

all of equal importance !

h1(x) decouples from leading twist DISbecause helicity of quark must flip

NO MIXTURE WITH GLUON

g(x,Q2)=

g(x,Q2)=

and of course Gluons

inclusiveinclusive

Precision DIS data Precision DIS data PDFs PDFs

Un

po

lari

zed

DIS

Str

uct

ure

Fu

nct

ion

(x,Q

2 )

Parton Model F2

p(x,Q2) = ½ ei2[qi (x,Q2) + qi (x,Q2)]

Only half the integral momentum of a high-energy proton comes from q and q;

scaling violations constrain the gluon (x,Q2)-dependence.

however, still big uncertaintyfor G(x) at large x !

Polarized DIS dataPolarized DIS data

Only ~20-30% of proton spin arises from q and q helicity preferences

(); limited info on scaling violations, on shape or integral of gluon helicity preference g(x,Q2).

g1p = ½ ei

2 [qi (x,Q2) + qi (x,Q2)] Parton Model

THE COMPASS THE COMPASS SPECTROMETERSPECTROMETER

Scifi, Silicon

SM1

SM2RICH1

Polarised Target

E/HCAL1

Muon Wall 1

Muon Wall 2,MWPC

SPS 160 GeV beam

Micromegas, SDC, Scifi

Straws, Gems

MWPC, Gems, Scifi, W45 (not shown)

E/HCAL2Hodoscopes

A1 and g1 deuteronA1 and g1 deuteron Windmolders

Windmolders

New analysis of g1 dataNew analysis of g1 data Stamenov

Stamenov

Although both our and DGLAP formulae lead to x- asymptotisc ofRegge type, they predict different Q2 -asymptotics: our predictionIs the scaling

2/222 1 /~g

xQwhereas DGLAP predicts the steeper x-behavior and the flatter Q2 -behavior:

)(21 )(ln(1/x) ~ Qg DGLAP

x-asymptotics is checked with extrapolating available exp data to x 0.

Agrees with our values of Contradicts DGLAP

Q2 –asymptotics has not been checked yet.

our calculations

DGLAP fit

Conclusion: Small x behaves as perturbative !

ErmolaevSStructure of standard DGLAP inputs for initial tructure of standard DGLAP inputs for initial

parton densities and the role of the singular termsparton densities and the role of the singular terms

Gluon Polarization Gluon Polarization GG

RHIC: the “Polarized” ColliderRHIC: the “Polarized” Collider

BRAHMS & PP2PP

STARPHENIX

AGS

LINACBOOSTER

Pol. Proton Source

Spin Rotators

Strong Snake

Siberian Snakes

200 MeV polarimeter

AGS inelastic polarimeter

Rf Dipoles

RHIC pC “CNI” polarimeters

PHOBOS

RHIC

absolute pHpolarimeter

SiberianSnakes

During 2005 run:~ 50% Polarization Lmax = 1031 s-1cm-2 @ s 200 GeV

AGS pC “CNI” polarimeter

Partial Snake

The RHIC ExperimentsThe RHIC Experiments

STAR

BRAHMS

pp2pppolarimeters

Hadron – Hadron CollisionsHadron – Hadron Collisions

ˆˆˆ LLa

factorization !D(z)

P1

P2

S1

S2

qgqgge ̂:..for most processesNLO calculations / predictions available

ALL a

ab

b ˆ (

a

b c X)

00 and prompt- and prompt- -section @ -section @ = = 00

prelim

inar

y

-section result consistent withNLO pQCD calculationsover 8 orders of magnitudefavors a larger gluon-to-pion FF

pp+Xppo+X

important confirmation of theoretical foundations for spin program

pQCD describes result very well !

Kawall & Okada

First First AALLLL measurement inclusive measurement inclusive

p + p o + X, ~ 0

gqgq

qqqq

gggg

o

pT (GeV/c)

● `03 + `04 combined

inclusive o production:mixture of gg / gq / qqscatteringspT dependence

expect much more precise data andlarger pT range (`05 run)

prelim

inar

y

G from Incl. JetsG from Incl. JetsMixture of gg / gq / qq scatterings

– sensitive to gluon polarization

– large -section high statistics with low L

– reconstruct JETS via TPC pT for charged

hadrons + EMC ET for EM showers

p+p, s=200 GeV STARSTAR

jet cone=0.4, 0.2<jet<0.8

prelim

inar

y

gggg

gqgq

qqqq

G

G

G

G

q

q

q

q

G

G

q

q

Hallman

Prompt Photon ProductionPrompt Photon Production

Gluon Compton dominates Small Background from

Annihilation No fragmentation contribution at

LO)(

)(

)(

)(

)(

22

22

1

1 qgqaxqe

xqe

xg

xgA LL

ii

i

ii

i

LL

large quark polarization for x > 0.2 large analyzing power

A1

Hallman

BedferG

Bedfer

Bedfer

semi – inclusivesemi – inclusiveandand

quark polarizationquark polarization

B. Dressler et al. Predictions

s = 500 GeV

s = 500 GeV

SIDIS sensitivity reduced by fragment- ation functions and eq

2 weighting

qq (flavor) Sea Polarizationqq (flavor) Sea Polarization

Semi-Inclusive DIS: e + N e’ + h + X

W ± Production at RHIC

{

{

27.6 GeV e+/e-

The HERMES experimentThe HERMES experiment

0.002 < x < 0.9 0.1 < Q2 < 15 GeV2

p/p ~ 1-2% < 0.6 mrad

Lepton ID with ~98%Hadron contamination <0.5%

Contalbrigo

)Q,(q

q

(z)Ddz)Q(x,q'e

(z)Ddz)Qq(x,e)Q(x,A 2

qq'

hq'

22q'

hq

22q2h

1 x

In semi-inclusive deep inelastic

scattering the hadron tags

the flavour of struck quark

Derive purity of tag from unpolarized data (fragmentation functions)

Hadron asymmetries (measured)

Known quantities(from other data)

Polarized Parton Distribution Functions

!

QPA

Flavour decomposition of spinFlavour decomposition of spinKey issue: role of sea quarks in nucleon spin

results perfectly consistent with inclusive fits: 2/dof =0.6…1.6 for BB(SU3-sym) and GRSV-valence

Quark polarisationsQuark polarisations

first 5-flavour extraction

[PRL92, 012005, 2004; PRD71, 012003, 2005]

• no significant sea quark polarisation

• in measured x-range (0.023-0.6):

0.0430.002 u -

0.0350.054 d -

0.0340.028 s

Contalbrigo

Difference Asymmetry in SIDISDifference Asymmetry in SIDISChristova

Christova

Flavor-Tagged Quark Polarizations via Flavor-Tagged Quark Polarizations via WW PV in W production

W produced through pure V-Achirality is fixed !

+ no fragmentation ambiguity limited x range

AL~u/u(x) ~ 0.7-0.9 at large-x

Requires large luminosity ands = 500 GeV

)()()()(

)()()()(

baba

babaWL xuxdxdxu

xuxdxdxuA

Transverse SpinTransverse Spinin hadronic interactionsin hadronic interactions

Transverse Single Spin Transverse Single Spin AsymmetriesAsymmetries

Fermilab E-704 reported Large Asymmetries AN Could be explained as

– Transversity X Spin-dependent fragmentation (Collins effect),

– Intrinsic-kT imbalance + Lq (Sivers effect)

GeV 4.19at sXpp

Sivers vs. CollinsSivers vs. Collins

Sivers effect [Phys Rev D41 (1990) 83; 43 (1991) 261]:Correlation between the proton spin (Sp), momentum (Pp) and transverse momentum (kT) of the unpolarized partons inside. The unpolarized parton distribution function fq(x,kT) is modified to:

Collins effect [Nucl Phys B396 (1993) 161]:

Correlation between the quark spin (sq), momentum (pq) and transverse momentum (kT) of the pion. The fragmentation

function of transversely polarized quark q takes the form:

qPP

qpPqq

NqqqPqq

)()k(x,ƒΔ

21

)k(x,ƒ),(x,ƒkPS

kPSSk

πq

πqqNqπ

kp

kpssk

)()k(z,D)k(z,D),(z,D /q/q/q 2

1ˆ

Melis

Melis

Melis

• pQCD calculations consistent with measured large- cross sections

• transverse single-spin effects observed for s = 200 GeV pp collisions large xF

Collins effect transversity Sivers effect orbital angular momentum

Forward Forward 00 Production p Production p+p +p oo+X+XSTARSTAR

prelim

inary

Morozov

prelim

inary

AANN(p(pTT) in run3+run5 at ) in run3+run5 at √s=200 GeV√s=200 GeV

Combined statistics from run3 and run5 allowed to distinguish nonzero effect in AN(pT) plot

There is an evidence that analyzing power at xF>0.4 decreases with increasing pT

Theoretical prediction’s needed to compare – constrain on Sivers function?

STARSTAR

Morozov

AANN of Jet k of Jet kTT

STAR projections for 30 pb1 (4pb-1), Pbeam=70% (50%)

pp di-jet + X s = 200 GeV 8 pT(1,2) 12 GeV |(1,2)| 1.0

D.

Bo

er

& W

. V

og

els

an

g

pre

dic

tion

s

Search for spin-dependent transverse motion preferences inside proton (related to parton

Lorbit ) via predicted spin-dependent deviation (not power-suppressed) from back-to-back

alignment of di-jet axes study unique to RHIC spin: Access Sivers function

0

2

h

A probe to access to Sivers functions (=left/right asymmetry in the kT of the partons ).

Hallman

What about What about polarization … polarization …E 704

Transversity andTransversity andTransverse SpinTransverse Spin

in leptoproductionin leptoproduction

Tensor charge (’91 – ’92):

in analogy with:

Soffer inequality (95):

Leader sum rule (04):

in analogy with:

TransversityTransversity

In the last ten years: great development in

the theory of transversity remarkable role of

ΔTq(x), notably complementary to Δq(x)

In the last few years: role of the kt structure

functions clarified (Cahn and Sivers effects, …) )()(

2

1)( xqxqxq TT

)()( xqxqdxg TTT

)()( xqxqdxg A

gqq

zqq

T Lxqdx,,,

)(2

1

2

1

zz LGS 2

1

Key features of transversity:• probes relativistic nature of quarks• no gluon analog for spin-1/2 nucleon• different Q2 evolution and sum rule

than Δq(x)• sensitive to valence quark

polarization

Measuring Measuring ΔΔTTq(x)q(x)

Hard scattering (e.g. GSI)

–Drell-Yan

Hard scattering (e.g. RHIC)

–Drell-Yan

–Single Spin Asym (e.g. p↑p→X)

SIDIS(e.g. COMPASS and HERMES )

Chiral-odd: requires another chiral-odd partner

FF (x) qΔT

q Δ qΔ TT NN NN

q Δ qΔ TT

Inclusive DIS ppl+l-X

lpl’hX

impossible direct measurementΣΔTq(x) ·ΔTq(x)

convolution withspin dependentfragment. func.

lpl’h1h2X

Bradamante

Transversity MeasurementTransversity Measurement

Drell-Yan production of lepton pairs– clean, but requires high

luminosity

– combination of q and q

– large analyzing power aTT

but q small

* / Z

l+

l

ii

ii

TTTT xqxqe

xqxqeaA

)()(

)()(

21

2

21

2

Efremov

Prokudin

Efremov

COLLINS and SIVERS COLLINS and SIVERS

ASYMMETRIESASYMMETRIES2002 data only

systematic errors are smaller than the quoted statistical errors

Collins

Sivers

Bradamante

Deuteron target

Collins and Sivers MomentsCollins and Sivers MomentsKorotkov

proton target

Prokudin

SIVERS ASYMMETRIESSIVERS ASYMMETRIESCOMPASS2002 data

M. Anselmino, M. Boglione, U. D'Alesio, A. Kotzinian, F. Murgia and A. ProkudinExtracting the Sivers function from polarized SIDIS data and making predictionsarXiv:hep-ph/0507181

Bradamante

Efremov

Sissakian

Prokudin, Efremov,Sissakian

Efremov

G P D sG P D sand Land Lqq

Kroll

Kroll

t 0

Kroll

uV quarksdV quarks

Kroll

Experimental access to GPDsExperimental access to GPDs

Exclusive meson electroproduction:

– Vector mesons (0):

– Pseudoscalar mesons ():

Deeply virtual Compton scattering (DVCS):

),,( and ),,( txEtxH ),,(

~ and ),,(

~txEtxH

DVCS Bethe-Heitler

)()( 22BH

*DVCSDVCS

*BHDVCSBH ττττ||τ||τeNeNdσ

Experimental access to DVCSExperimental access to DVCS)()( 22

BH*DVCSDVCS

*BHDVCSBH ττττ||τ||τeNeNdσ

Beam-Spin Asymmetries in DVCSBeam-Spin Asymmetries in DVCS

Proton Deuteron

Contalbrigo

Transverse Target-Spin Asymmetries in DVCSTransverse Target-Spin Asymmetries in DVCS

Sensitive to Ju

Contalbrigo

elastic scatteringelastic scattering

AANN for for ppp p pp pp @ 100 GeV @ 100 GeV

prel

imin

ary Im r5 = 0.002 0.029

Re r5 = -0.006 0.007

2/ndf = 10 / 12

uncertainty on the( = 0.03) parametercan change at the same level

hadhad

p

had

m

tsr 3155 2)(

with hadronic

spin-flip

stat + sys errors used in fits

hadronic spin – flip contribution consistent with zero (1 level)

in the simplest assumption:spin-flip prop. to non-flip ampli.

Bravar

4321*52 Im

4),(

sdtd

tsAN

NA

AANNNN for for pppp pp pp @ 100 GeV @ 100 GeV

prel

imin

ary

source ofsystematic errors:

1 PT2 = 3 %

2 from backgrounds and event selections

~ 0.0013 rel. luminosity ~ 0.001

similar to stat. errors

NNB

T

TBTNN PPP

A

2

11

ANN basically 0 double spin – flip amplitudes (2 and 4)

are very small / do not contribute in this region

statistical errors only

Bravar

Elastic Elastic pppp Scattering Scattering s = 200 GeVs = 200 GeV

Preliminary

r5 e5 im5 m5

t Im

Kanavets

spin technology:spin technology:

acceleration of polarized proton beamsacceleration of polarized proton beams

polarized sources and targetspolarized sources and targets

polarimeterspolarimeters

Spin Precession in Laboratory Frame:(Thomas [1927], Bargmann, Michel, Telegdi [1959])

dS/dt = (e/m) [(GB + (1+G) B] S G = 1.91 E

Lorentz Force

dv/dt = (e/m) [ B ] v

For pure vertical field Spin rotates Gtimes faster than motion, sp = G

Spin depolarization resonances due to transverse magnetic fields:

Imperfection resonance (magnet errors and misalignments, closed orbit errors, …):G = sp = n

Intrinsic resonance (vertical focusing fields - quadrupoles, finite beam emittance, …):

G = sp = Pn ±y

Spin DynamicsSpin Dynamics

B

S

v

Shatunov

Siberian Snake OperationSiberian Snake Operation

Partial Snake (AGS)– rotate around beam direction

– compensate for imperfections

– use an RF dipole to compensate forintrinsic resonances

Full Snake (with 2 rotators - RHIC)– rotate around two orthogonal

axes in the accelerator plane(i.e. x and y comp. separately)

– compensate for imperfectionsand intrinsic resonances

Siberian “ Snake ”Siberian “ Snake ”

Invented in 1974 by Derbenev and Kondratenko

Beam Trajectory while rotating Spin Direction~ 3D image of “snake”

AGS Polarization during AGS Polarization during accelerationacceleration

raw

asy

mm

etry

= A

N

PB

12+ 36- 36+G = 1.91 Ebeam

depolarizing

resonances:

intrinsic: G =

imperfection: G = n

each point = 50 MeV step

48-

red line: simulation of polarizationlosses assuming constant AN

Imperfection Resonances: Imperfection Resonances: GG = n = npartial snake (AGS) =imperfection resoance

if snake sufficiently strong (5% enough in AGS) spin is fully flippedwhen crossing an imperfection resonance with no polarization loss

for G n, spin “oscillates” around stable direction, which is tilted from the vertical

S

S

S

SS

S

G = n G = n + 1/2

1

2

3

Intrinsic Resonances: Intrinsic Resonances: GG = n = nPP + +

S

S

N

N

quadrupole

betatron oscillation of frequency

if spin precession “in phase” with

betatron oscillation G = when crossing the quadrupoledepolarizing kicks adddepolarizing resonance condition

Q

Q

Q Q

FODO section

“AGS”

to be in phase with betatron oscillation over a closed orbit spin must precess n + times

in a periodic accelerator spin “in phase” with betatron oscillation when crossing same quadrupole in consecutive FODO section if

G = nP + Polarization losses reduced / avoided by forcing a full spin reversal (flip) usingan RF dipole

OPPIS High Intensity HOPPIS High Intensity H Source Source

> 80 %polarization

15 1011

protons / pulseat the source(500 A, 300 s)

6 1011

protons/pulseat end of LINAC

COMPASS OD magnetCOMPASS OD magnet

Solid angle:

from 70 mradto 180 mrad

+30% FOM

2006: new target magnet by OD

The Atomic H Beam The Atomic H Beam SourceSource

separationmagnets(sextupoles)

H2 dissociator

Breit-Rabipolarimeter

focusingmagnets(sextupoles)

RF transitions

holding field magnet

recoil detectorsrecord beam intensity100% eff. RF transitionsfocusing high intensityB-R polarimeter

OR

Pz+ OR Pz

-

H = p+ + e-

Setup for Setup for ppC scattering – C scattering – the RHIC the RHIC polarimeterspolarimeters

recoil carbon ions scattered around 90o

detected with Silicon strip detectors

polar acceptance± 1.5o around 90o

2 72 channels read out with WFD

very large cross section very fast measurements

statistics per measurement (~ 20 106 events) allows detailed analysis

beamdirection

1

34

5

6

RHIC 2 rings

2

Si strip detectors(ToF, EC)

~36cm

Ultra thin Carbon ribbon Target

(3.5g/cm2 , < 10m)rightleft

rightleft

NB NN

NN

AP

1

recoil

Alekseev

futurefuture

J-PARCJ-PARC(Japan-Proton Accelerator Research Complex)(Japan-Proton Accelerator Research Complex)

High intensity proton machine @ 50 GeV

Saito

Spin physics program in the U70 polarized proton beam:Spin physics program in the U70 polarized proton beam:

1. AN and ANN in elastic scattering [high pT2]

2. Precision measurement of single-spin asymmetry in inclusive charged hadron production in pp and pA collisions at different production angles

3. Miscellaneous spin parameters (A,DNN,ALL) in hyperon production

4. Transversity in Drell-Yan muon pairs

5. Double-spin asymmetry ALL in Charmonium production (∆G/G gluon polarization through 2 if gluon-gluon fusion is significant)

Vasiliev

Alessandro Bravar

Facilty for Antiproton and Ion Research (GSI, Darmstadt, Germany)

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

Contalbrigo

Principle of spin filter methodPrinciple of spin filter methodP beam polarizationQ target polarizationk || beam direction

σtot = σ0 + σ·P·Q + σ||·(P·k)(Q·k)

transverse case:

Q0tot

longitudinal case:

Q)( ||0tot

For initially equally populated spin states: (m=+½) and (m=-½)

Unpolarized anti-p beam

Polarized H target

Contalbrigo,Nikolaev

Conclusions ?Conclusions ?Very very exciting “spin” times are ahead of us !

In the next year expect plenty of new data from RHIC, COMPASS, et al.

It has been a very nice week here in Dubna !

Thanks again to Anatoli for organizing this very exciting workshop !

Hope to see each other in Kyoto - Spin06 and again in Dubna in ’07 !

Have a safe trip home !

Thank you for your patience andmy sincere apologies to all that have not been mentioned in my talk

Sandro