Transcript Document

Comparative study of the specific
charge hadron in electron SIDIS
off proton and deuteron
Ben-Hao Sa
China Institute of Atomic Energy
Central China normal University
It was done in collaboration with
CCNU:
Dai-Mei Zhou
Yun Cheng
Xu Cai
CIAE:
Yu-Ling Yan
Xing-Long Li
Xiao-Mei Li
Bao-Guo Dong
benefit
Contents
• Introduction
• Brief description for PACIAE
• Results
• Conclusion
Introduction
Sketch of lowest order (Born approximation)
e-p deep inelastic scattering (DIS)
q2 = -Q2
q2 = -Q2
h
NC
h
CC
IDIS (inclusive deep inelastic scattering) in which
all accessible states X & h, all possible outgoing
momenta, are included. Remainder is only the
scattered electron
SIDIS (semi-inclusive deep inelastic scattering)
is the same as DIS but includes a specific type
of hadron in addition
IDIS: an impotent & hot frontier in between
particle & nuclear physics since eightieth of last
century. It plays a crucial role in the field of
• Confinement of quark and gluon in hadron,
such as PDF, FF, &  s extractions, as well
as searching for Higgs boson, SUSY, etc.
• Hadronization processes
space & time evolutions, energy loss, etc.
• eRHIC (e-p,CM energy 45 – 175 GeV),
LHeC (e-p, CM energy more than 1 TeV),
and EIC
nDIS era
We, extend PACIAE for l-p and l-A, Confront
Second order e-p DIS Feynman diagram
Complete e-p NC differentia
cross section may be factorized as
d
d
QED
weak
=
（
1+

)(1


)
2
2
dxdQ
dxdQ
2
2
Born
d
4 F2 ( x)
Mxy
2

[
(1

y

)

F
(
x
)
y
]
1
2
2
dxdQ
Q
x
2E
2
Born
2
 QED : QED radiative correction
 weak : weak radiative correction
(similar for CC)
Two independent variables:
in the past: (E', )
presently: (xB ,Q2); or (xB ,W2); or (xB ,y)
HERMES e- SIDIS off p & D experiments
HERRMES -> specific charged hadron yield of
pi+,pi-,K+,K- in DIS is crucial for reliable
extraction of FF with
distinguished
from
HERMES corrects measured yield of type h
hadrons for:
limitation in geometric acceptance
radiative effect
detector resolution
Born-level yield is then resulted. Normalizing it
by DIS yield (yield of scattered e-) they obtain
Polar angle
for the normalized hadron yield as a function of z
Brief description for PACIAE
1) Initiation
PYTHIA 6.4 vs. PACIAE2.0
Nucleons in colliding nucleus, distributed
according to Woods-Saxon distribution
 Paticipant nucleons, to be inside OZ
 Spectator nucleons, to be outside OZ
but inside nucleus system
 Projectile nucleons (in Lab. frame):
px=py=0, pz=pbeam
 Target nucleons (in Lab, frame)
px=py=pz=0
 Decompose nucleus-nucleus colli. ->
NN collisions according to straight-line
trajectories & NN total x-section

Describe each NN collision by PYTHIA with
string fragmentation switched-off &
qq (q q ) broken into q pair ( q pair)
 A partonic initial state is obtained after all NN
collisions are exhausted

2) Parton rescattering (PRS)
• PRS is performed by MC method
• 2->2 LO perturbative QCD x-section is
used
3) Hadronization
Two options are provied for hadronization
• Lund string fragmentation
• Phenomenological coalescence model
4) Hadron rescattering (HRS)
Usual two body collision model is used
 Only some hadrons are considered

& their anti-particles
Some specials
• For p+p & p+A (A+p), OZ is not introduced
• l+p & l+A are dealt like p+p & p+A,respectively
• As l+p x-section is a few order of magnitude
lower than p+p, incident lepton is probably
only one colliding with nucleon when it passes
through the target
• Strike nucleon is the one with lowest
approaching distance from incident lepton
Results
1. Comparison with data and other theories


HLMC: composed of
Lepto e-p event generator <- JETSET 7.4 & PYTHIA 5.7
Program for detector simulation
Event reconstruction
where thirteen parameters were tuned to the
yield as function of z, pT, & \eta
LOQCD:
in factorization theorem framework: PDF, hard
scattering x-section, & FF
in quark parton model: hadron yield is a
convolution of PDF & FF
2. Effect of α and β
3. Effect of PRS & HRS
4. Effect of SQSF
Conclusions
Default PACIAE reproduced HERMES data
nearly as well as HLMC where thirteen
paramters were tuned
 Normalized yield increases (decreases) with
increasing α and β
 Effect of PRS & HPS is visual, former>later,
due to interacting volume & # of particles
 Effect of SQSF is obvious. It is possible to
improve the agreement between HERMES &
PACIAE by adjusting SQSF
 Effects are expected to be increased with
increasing target size

Thank you very much
hadron,(Eh,pl,pt)
direction of virtual photon
selected in order of Eqs. 2,1,3,4,5,6,7,& 8
III) HERMES results: 27.6 GeV e- beam on A
>4 GeV
z > 0.1
taken from Nucl. Phys. B780(2007)1
Theoretical models
1) Phenomenological models:
Formation time/legth
Absorption cross section
NP, B291(1987)793; NP, B346(1990)1;
Z. Phys. C56(1992)493;
Eur. Phys. J. C44 (2005)219;
hep-ph/0205123
arXiV:1310.5285
2) QCD-inspired models:
Partonic rescattering (energy loss)
NP, B483(1997)291; NP, B484(1997)265;
PRL 85(2000)3591; PRL 89(2002)162301;
JHEP 0211(2002)44; NP, A720(2003)131;
Eur. Phys. J. C30(2003)213; arXiV:09073534;
NP, A761(2005)67; PR, C81(2010)024902
3) PYTHIA + BUU simulation
Formation time/length
Hadronic rescattering
PR, C70(2004)054609; NP, A801(2008)68
4) PACIAE
Partonic initiation for eA collisions
Praton rescattering
hadronization
hadron rescatering
As both partonic and hadronic rescatterings
are considered in PACIAE, experimental
results may be better studied by PACIAE
Plan for studying A dependence of ratio
• Comparing with HERMES data
• Predecte for LHeC (60 or 140 e- beam energy)
• Utilize <z>, <Q2>, … (cf. NP,B780(2007)1) &
same experimental constraints (Lorentz
invarience)
Sketch of ep deep inelastic scattering
 EE
black box,hints for QCD
processes: vacume
excitation,parton shower,
resattering,etc.
'
 Q 2  q 2  (k  k ' ) 2
z  Eh /
e(K’,E’ )
h
first
(born)
X
q=-Q2
e(K,E)
;… *
 EM
h
(q, )
 EM
second
 EM
+
+
 EM
 EM
X
 EM
p(p)

…
Exchange Z,W+,and W-,bosons either
A sketch for an exposing of black box
struck quark
fragments