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Radiative Corrections for Heavy Nuclei

Radiative Corrections for Heavy Nuclei. Precision Measurement of F L with the EIC. F L ~ a s G(x,Q 2 ): the most “direct” way to G(x,Q 2 ). F L needs various √s  longer program. In order to extract F L one needs at least two measurements of the inclusive cross section with a

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Radiative Corrections for Heavy Nuclei

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  1. Radiative Correctionsfor Heavy Nuclei EIC INT Program, Seattle 2010 - Week 5

  2. Precision Measurement of FL with the EIC FL ~ asG(x,Q2): the most “direct” way to G(x,Q2) FL needs various √s  longer program In order to extract FL one needs at least two measurements of the inclusive cross section with a “wide” span in inelasticity parameter y (Q2=sxy) Coverage in x & Q2 for inclusive cross section measurements Plots for 4 GeV electrons on 50 – 250 GeV protons EIC INT Program, Seattle 2010 - Week 5

  3. Measuring FL with the EIC Lets get a feeling for systematic uncertainties 1% energy-to-energy normalization • 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 FL for fixed electron energy (4GeV) and proton energies: 50, 70, 100, 250 GeV Luminosity: 4fb-1 each setting EIC INT Program, Seattle 2010 - Week 5

  4. Measure gA(x) impact parameter dependent • Stringent requirements on: • Momentum resolution • t resolution and range A. Caldwell, H. Kowalski Phys.Rev.C81:025203,2010 Radiative Correction will impact them EIC INT Program, Seattle 2010 - Week 5

  5. Some Info on RadCors final vacuum loops initial EIC INT Program, Seattle 2010 - Week 5 • Inclusive cross section • stot = sela + sqela + sinel + sv • 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 bremsstrahlung • radiation 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?

  6. Why are RadCor important? events smeared into acceptance EIC INT Program, Seattle 2010 - Week 5 • 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

  7. RadCor and smearing unfolding in MC generate observed kinematics xmeas, Q2meas Radiative Correction Code no photon radiated photon radiated xtrue=xmeas, Q2true=Q2meas calculate xtrue, Q2true hand kinematics to generator (lepto, pythia, ..) What subprocess is generated is regulated by phase space Hand particles to GEANT EIC INT Program, Seattle 2010 - Week 5

  8. What do we know? EIC INT Program, Seattle 2010 - Week 5 • A lot of radiative correction codes for proton • much less existing for eA • all experiments apart from HERMES had m-beams • suppressed radiation • HERMES 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.gz • QED radiative processes in electron-heavy ion collisions at HERA K. Kurek http://www.desy.de/~heraws96/proceedings/nuclei/Kurek.ps.gz

  9. What do we know? • 10-4 < x < 10-3 and 27.5 GeV x 410 GeV Pb S C He D • solid: inelastic rad. corrections • dashed: inelastic, quasi-elastic and elastic rad. corrections Huge effects at high y EIC INT Program, Seattle 2010 - Week 5

  10. What do we know? Compton peak relevant if momentum transfer to nucleus very small effect of nuclear form factor included EIC INT Program, Seattle 2010 - Week 5

  11. What do we know? • Two photon exchange two photon exchange only important for very heavy nuclei EIC INT Program, Seattle 2010 - Week 5

  12. Can we suppress things? S C He D Need a code, which puts all together to make full calculations need to test analysis strategies to suppress rad. corrections EIC INT Program, Seattle 2010 - Week 5 • 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

  13. and Summary • 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 EIC INT Program, Seattle 2010 - Week 5

  14. BACKUP EIC INT Program, Seattle 2010 - Week 5

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