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Transcript of Alessandro Bravar S U M M A R Y XI th Advanced Research Workshop Spin-05, Dubna, September...
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