Transcript MC studies of a new Trigger

SUMMARY OF THE SPIN
SESSION
EXPERIMENT PART
Andrea Bressan
University of Trieste
Who is who?
Hall B
STAR
Hall A
Large acceptance spect.
electron/photon beams
Two high-resolution
4 GeV spectrometers
Beam: ≤6 GeV e-; 85% polarization
Beam: 27.5 GeV
e±; <50>%
polarization
6LiD,
Beam:
160
GeV3He,
m; 75%
polarization
Target:
polarized
targets
NH3
Hall C
6
50%
polarization
Target: (un)-polarized gasTarget:
targets;LiD;
<85%>
polarization
7 GeV spectrometer,
1.8 GeV spectrometer,
large installation experiments
7/21/2015
Beams: 250 GeV pp; <60>% polarization
Lumi: 1.2 1031cm-2s-1
Andrea Bressan
2
What we are after?
Naïve parton model
uv 
4
3
d v   13
BUT
1989 EMC measured
 = 0.120 0.094 ± 0.138
±
Spin Puzzle
Unpolarised structure fct.
Gluons are important !
G
Sea quarks qs
Full description of Jq and Jg
needs
orbital angular momentum
11 11
1 1
 ((uuvv dd(vvu
qqss))dvL
)G
v
q  G  Lg
22 22
2 2
(us  d
s   u   d  s   s )
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Andrea Bressan
3
COMPASS:
Valence PDFs


A /  














( h   h )  ( h   h )






( h   h )  ( h   h )


For LO:
Ad

 
( x )  AdK

K 

uv ( x )  d v ( x )
uv ( x )  d v ( x )
Assuming:
1
1
1N  (a0  a8 )
9
4
1
 v   ( uv ( x )  d v ( x ))dx
0
1
1
u  d  31N   v  a8
2
12
1
 (  s   s )  ( a8   v )
2
7/21/2015
v is 2.5stat away from flavour
symmetric sea scenario
Andrea Bressan
4
HERMES: polarized and unpolarized sPDF
K
K
 Dn str . ( z )dz  4 D( z )u

K
dz   D( z )dK

K
D
( z )dz  2 D( z ) sK
K
strange
dz

K
Need longitudinal polarized deuterium target
strange quark sea in protonKand neutron
identical
K
K
Fit x-dependence of multiplicities
dN ( x ) / dx Q( x ) Dn str . ( z )dz  S ( x )  Dstrange ( z )dz
fragmentation simplifies dN Dis ( x ) / dx 
5Q( x )  2 S ( x )
to get S(x) PDF and Kaon FF
dz
All needed information can be extracteddotted:
from HERMES data alone
K
HERMES
Preliminary
2)and kaon AK
2) double
CTEQ-6L
&
fit
D
( z )dz
inclusive
A1,d(x,Q
(x,Q
spin
asym.
1,d
S
Kaon multiplicities  DQK and DSK
K
dashed:
D
Q

( z )dz
Only assumptions used:
isospin symmetry between proton dashed-dotted:
and neutron
charge-conjugation invariance in fragmentation
solid:
K
D
 S ( z )dz
S(x)= x  a1 e  x / a2 (1  x )
Q(x): CTEQ-6L & DSS
S ( x )  k (u  d ) / 2
s(x) + sbar(x)
7/21/2015
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Kaon Asymmetry
Inclusive Asymmetry
HERMES: polarized and
unpolarized s-PDF

0.6
0.02

7/21/2015
0.6
0.02
e  d  e' K  X
Q  0.359  0.026  0.018
S  0.037  0.019  0.027
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GLOBAL FIT
deFlorian, Sassot, Stratmann, Vogelsang
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Measuring G
7/21/2015
Andrea Bressan
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ALL from STARS jets
7/21/2015
Andrea Bressan
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ALL from 0,±, at phenix
7/21/2015
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10
COMPASS OPEN CHARM
7/21/2015
Andrea Bressan
11
COMPASS HIGH-pT
7/21/2015
Andrea Bressan
12
The 3rd Twist-2 structure
function
three quark distribution functions (DF) are necessary to describe
the structure of the nucleon at LO
q(x)
f1q (x)
unpolarised DF
quark with momentum xP in a nucleon
well known – unpolarised DIS
 vector charge
q(x)
g1q(x)
 axial charge
quark with spin parallel to the nucleon
spin in a longitudinally polarised nucleon
known – polarised DIS
Tq(x) = q↑↑(x) - q↑↓(x)
h1q(x),
transversity DF
 tensor charge
7/21/2015
helicity DF
quark with spin parallel to the
nucleon spin in a transversely
polarised nucleon
largely unknown
ALL 3 OF EQUAL IMPORTANCE
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13
Transversity DF
Tq(x) = q↑↑(x) - q↑↓(x)
h1q(x),
dq(x),
dTq(x)
q=uv, dv, qsea
quark with spin parallel to the
nucleon spin in a transversely
polarised nucleon
Properties:
• probes the relativistic nature of quark dynamics
• no contribution from the gluons  simple Q2 evolution
• Positivity: Soffer bound…………….. 2 | ΔTq |  q + Δq Soffer, PRL 74 (1995)
• first moments: tensor charge……….Δ q   dx Δ q(x)
T
T
• sum rule for transverse spin
1 1
in Parton Model framework…………   T q  Lq  Lg
2 2
Bakker, Leader, Trueman, PRD 70 (04)
• it is related to GPD’s
• is chiral-odd: decouples from inclusive DIS
7/21/2015
Andrea Bressan
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Collins Final on Deteron COMPASS
Federica Sozzi
7/21/2015
Andrea Bressan
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Collins FF from Belle
7/21/2015
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Global Fit
7/21/2015
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Global Fit
For Collins FF and Transversity  Andreas Metz
7/21/2015
Andrea Bressan
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Final 2-hadron from
Hermes
Xiaorui Lu
7/21/2015
Also Measurements from COMPASS on Deuteron… F. Sozzi
Andrea Bressan
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SIVERS Mechanism
 The Sivers DF
Δ0T q is probably the most famous between TMDs…
 gives a measure of the correlation between the transverse momentum and
the transverse spin
 Requires final/initial state interactions of the struck quark with the spectator
system and the interference between different helicity Fock states to survive
time-reversal invariance
 Time-reversal invariance implies:
Δ0T q (x,k T2 )SIDIS   Δ0Tq (x,k T2 )DY
…to be checked
 In SIDIS:
Nh  S   Nh0   1  AhS  sin S
7/21/2015

ASiv 
Andrea Bressan
h
S
A

f  PT
 e  Δ qD
 e  qD
q
2
q
q
T
0
2
q
h
q
h
q
20
Sivers Final on Deuteron
from COMPASS
7/21/2015
Andrea Bressan
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Global Analysis
Stefano Melis
For Sivers DF  Andreas Metz
7/21/2015
Andrea Bressan
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Global Analysis II
Stefano Melis
7/21/2015
Andrea Bressan
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7/21/2015
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AN() at √s = 62 GeV
Submitted to Physical Review Letters
arXiv:0801.1078
Twist 3
sivers
•
•
Large AN(): 0.3-0.4 at xF~0.6 pT~1.3 GeV
Strong xF -pT dependence. Though |AN()| ~ !AN()| |AN()/AN()|
decreases with xF-pT
DIS, London, April 7-11, 2008
25
Unifying 62 and 200 GeV
BRAHMS + E704
E704 data – all pt (small star) pt>0.7 red star.
DIS, London, April 7-11, 2008
26
The Hunt for Lq
Study of hard exclusive processes
leads toa new class of PDFs
Generalized Parton Distributions
H q , Eq , H q , Eq

possible access to
orbital angular momentum

1 1
J q   xdx H q  E q
2 1
1
J q    Lq
2
exclusive: all products of the reaction are detected
missing energy (E) and missing Mass (Mx) = 0
7/21/2015
Andrea Bressan

t 0
from DIS: ~0.3
27
GPDs Introduction
What does GPDs charaterize?
unpolarized
polarized
H q  x , , t  H q  x , , t 
H q ( x ,0,0)  q, H q ( x ,0,0)  q
conserve nucleon helicity
E q  x , , t 
E q  x , , t  flip nucleon helicity
not accessible in DIS
quantum numbers of final state
pseudo-scaler mesons
DVCS
q
q
q
H E
E
H
AC,ALU, AUT, AUL
7/21/2015
select different GPD
q
H q , Eq
AUT,+
Andrea Bressan
vector mesons
H q , Eq
AUT,r,,w
28
DVCS ASYMMETRIES


d  ~ *BH  DVCS  *DVCS  BH  |  BH |2  |  DVCS |2
 different charges: e+ e- (only @HERA!):
C ~ cosf ∙Re{ H
~
H
+ H +… }
polarization observables:
~
LU ~ sinf∙Im{H + H + kE}
~
UL ~ sinf∙Im{H + H + …}
UT ~ sinf∙Im{k(H - E) + … }
 = xB/(2-xB ),k = t/4M2
UTH
beam
target
~
H
H, E
kinematically suppressed
29
CLAS: BSA: coverage and f distributions
Data integrated over t
• 13 Q2, xB bins
• 5 t bins
• 12 f bins
Fit =  sinf/(1+cosf
Ph.D. Thesis of F.X. 30
Girod
CLAS: BSA: a vs. t
CLAS e1-dvcs
Hall A
CLAS @ 4.3 GeV2
VGG(*) twist-2 (DD)
VGG(*) twist-2 and 3
Regge model (**)
(*) Guidal, Polyakov, Radyushkin,
Vanderhaegen, PRD 72 (2005)
(**) Cano and Laget, PL B551 (2003)
GPD model
overestimates
the data
arXiv: 0711.4805 [hep-ex]
Submitted to PRL
Ph.D. Thesis of F.X. 31
Girod
Hermes: Transverse Target Spin Asymmetry
Sensitivity to Jq
32
Hermes: Charge and Beam Spin Asymmetry
Beam Charge Asymmetry
33
Hermes: Charge and Beam Spin Asymmetry
Beam Spin Asymmetry
DVCS Ampl.
Interference Ampl.
34
Hermes: Charge and Beam Spin Asymmetry Heavy Targets
Beam Charge Asymmetry
Beam Spin Asymmetry
Why nuclear DVCS:
constrain nuclear GPDs
constrain models attempting
to describe nuclear matter
neutron and proton matter
distribution in nuclei
35
What next?
 More data
Hermes/Compass/RHIC/Jlab
 New Data
Compass/RHIC…
 New Experiments
Jlab@12/CompassII
7/21/2015
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36
Thanks to all the
participants of the
Spin Session
[apologies to all speakers not covered in this summary]
7/21/2015
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… and pions
7/21/2015
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COMPASS 2-hadrons,
leading z-hadrons
7/21/2015
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39