E.C. AschenauerEIC INT Program, Seattle 2010 - Week 51.
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Transcript of E.C. AschenauerEIC INT Program, Seattle 2010 - Week 51.
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EIC INT Program, Seattle 2010 - Week 5 1
Radiative Correctionsfor Heavy Nuclei
E.C. Aschenauer
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EIC INT Program, Seattle 2010 - Week 5 2
Precision Measurement of FL with the EIC
E.C. Aschenauer
d2σ empNC
dxdQ2 =2pαem2 Y+
xQ4 (F2 −y2
Y+FL ±Y−
Y+xF3)
FL ~ αsG(x,Q2): the most “direct” way to G(x,Q2)FL needs various √s longer program
In order to extract FL one needsat least two measurements of theinclusive cross section with a “wide” span in inelasticity parameter y (Q2=sxy)
Coverage in x & Q2 for inclusivecross section measurements
Plots for 4 GeV electrons on 50 – 250 GeV protons
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EIC INT Program, Seattle 2010 - Week 5 3
Measuring FL with the EIC
E.C. Aschenauer
Conclusion from this study Dominated by sys. uncertainties gives max. luminosity here: 4fb-1 / A Depending on x & Q2 might be able to take a hit in luminosity need to include detector effects
Lets get a feeling for systematic uncertainties1% energy-to-energy normalization
FL for fixed electron energy (4GeV)and proton energies:50, 70, 100, 250 GeVLuminosity: 4fb-1 each setting
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EIC INT Program, Seattle 2010 - Week 5 4
Measure gA(x) impact parameter dependent
E.C. Aschenauer
Stringent requirements on: Momentum resolution t resolution and range
A. Caldwell, H. Kowalski Phys.Rev.C81:025203,2010
Radiative Correction will impact them
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EIC INT Program, Seattle 2010 - Week 5 5
Some Info on RadCors Inclusive cross section
σtot = σela + σqela + σinel + σv
for all parts photons can be radiated from the incoming and outgoing lepton, high Z-material Compton peak.
radiation is proportional to Z2 of target, like bremsstrahlungradiation is proportional to 1/m2 of radiating particle
elastic:
quasi-elastic: scattering on proton of nuclei proton stays intact nuclei breaks up
two photon exchange? Interference terms? E.C. Aschenauer
initial final vacuum loops
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EIC INT Program, Seattle 2010 - Week 5 6
Why are RadCor important? Modify kinematics Q2:
initial state: E’beam = Ebeam – Eg
photon goes along the beam line final state: E’out = Eout – Eg
photon goes somewhere in Calo
RadCor and detector smearing don’t factorize need to have RadCor implemented in MC to unfold
effects on kinematics unfolding in bins
Ntrue=Nmeas-Nbckg
E.C. Aschenauer
eventssmeared intoacceptance
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EIC INT Program, Seattle 2010 - Week 5 7
RadCor and smearing unfolding in MC
E.C. Aschenauer
generate observed kinematicsxmeas, Q2
meas
Radiative Correction Code
photon radiated no photon radiated
xtrue=xmeas, Q2
true=Q2meas
calculatextrue, Q2
true
hand kinematics togenerator (lepto, pythia, ..)
What subprocess isgenerated is regulated
by phase spaceHand particles
to GEANT
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EIC INT Program, Seattle 2010 - Week 5 8
What do we know? A lot of radiative correction codes for proton
much less existing for eAall experiments apart from HERMES had m-beams
suppressed radiationHERMES uses modified version of RADGEN (hep-ph/9906408v1)Radiative corrections to deep inelastic scattering on heavy nuclei at HERA
I. Akushevich and H. Spiesberger
http://www.desy.de/~heraws96/proceedings/nuclei/Akushevich.ps.gzQED radiative processes in electron-heavy ion collisions at HERA
K. Kurek
http://www.desy.de/~heraws96/proceedings/nuclei/Kurek.ps.gz
E.C. Aschenauer
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EIC INT Program, Seattle 2010 - Week 5 9
What do we know?
E.C. Aschenauer
dRC(A) =dσ A / dydσ B
A / dy−1 dRC(A)=
1+δRC(A)1+δRC(D)
−1
10-4 < x < 10-3 and 27.5 GeV x 410 GeV
solid: inelastic rad. corrections dashed: inelastic, quasi-elastic and elastic rad. corrections
Huge effects at high y
PbSC
HeD
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EIC INT Program, Seattle 2010 - Week 5 10
What do we know?
E.C. Aschenauer
Compton peak relevant if momentumtransfer to nucleus very small
(1−y)σinQe'=yσinQg
effect of nuclear form factor included
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EIC INT Program, Seattle 2010 - Week 5 11
What do we know?
E.C. Aschenauer
Two photon exchange
two photon exchange only important for very heavy nuclei
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EIC INT Program, Seattle 2010 - Week 5 12
Can we suppress things? elastic/quasi-elastic part: require some hadrons in
detector solid line: inelastic contribution
dashed line: after cuts Eg > 10 GeV E-pz from hadronic state is smaller
E.C. Aschenauer
Need a code, which puts all together to make full calculationsneed to test analysis strategies to suppress rad. corrections
SC
HeD
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EIC INT Program, Seattle 2010 - Week 5 13
Djangoh http://wwwthep.physik.uni-mainz.de/~hspiesb/djangoh
/djangoh.html is compiled at BNL and running
eA part is included need to do more studies HERACLES can be interfaced with other MC codes
HERMES code (RADGEN + eA version of lepto) is installed at BNL and close to run. No nuclear effects are included.
can compare results between eA-RADGEN with HERACLES can nPDFs be included?
Hubert Spiesberger is coming to INT next week, juhu E.C.
Aschenauer
and Summary
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EIC INT Program, Seattle 2010 - Week 5 14E.C. Aschenauer
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