E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5

1

Precision Measurement of F

L

with the EIC

F L ~



s G(x,Q 2 ): the most “direct” way to G(x,Q 2 ) F L



needs various longer program √s

d

2



NC e

m

dxdQ

2

p



2



2

em xQ

4

Y



In order to extract F inclusive cross section with a parameter y (Q 2 =sxy) L one needs at least two measurements “wide” span in inelasticity of the (

F

2



y

2

Y



F L



Y



Y



xF

3 ) Coverage in x & Q 2 for inclusive cross section measurements

E.C. Aschenauer

Plots for 4 GeV electrons on 50 – 250 GeV protons

EIC INT Program, Seattle 2010 - Week 5 2

Measuring F

L

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 & Q 2 able to take a hit in luminosity



need to include detector effects might be F L for fixed electron energy (4GeV) and proton energies: 50, 70, 100, 250 GeV Luminosity: 4fb -1 each setting

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 3

Measure g

A

(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

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 4

Some Info on RadCors



Inclusive cross section

  

tot =



ela +



qela +



inel +



v for all parts photons can be radiated from the incoming and outgoing lepton, high Z-material Compton peak.

radiation is proportional to Z 2 of target, like bremsstrahlung radiation is proportional to 1/m 2 of radiating particle elastic:

 

initial final vacuum loops quasi-elastic: scattering on proton of nuclei proton stays intact nuclei breaks up two photon exchange? Interference terms?

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 5

Why are RadCor important?



Modify kinematics

 

Q 2 : initial state: E’ beam = E beam – E

g

photon goes along the beam line



final state: E’ out = E out – E

g

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 N true =N meas -N bckg

E.C. Aschenauer

events smeared into acceptance

EIC INT Program, Seattle 2010 - Week 5 6

RadCor and smearing unfolding in MC

generate observed kinematics x meas , Q 2 meas Radiative Correction Code photon radiated no photon radiated calculate x true , Q 2 true x Q true 2 =x true meas =Q 2 , meas hand kinematics to generator (lepto, pythia, ..)

E.C. Aschenauer

What subprocess is generated is regulated by phase space Hand particles to GEANT

7

What do we know?



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

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 8

Pb S C He D

What do we know?



10 -4 < x < 10 -3 and 27.5 GeV x 410 GeV

  

RC

(

A

)



d d

 

B A A

/ /

dy dy



1



RC

(

A

)



1



1

  

RC RC

( (

A D

) )



1 solid: inelastic rad. corrections dashed: inelastic, quasi-elastic and elastic rad. corrections Huge effects at high y

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 9

What do we know?

Compton peak relevant if momentum transfer to nucleus very small (1



y

)sin



e

'



y

sin

 g

effect of nuclear form factor included

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 10

What do we know?



Two photon exchange two photon exchange only important for very heavy nuclei

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 11

Can we suppress things?

 

elastic/quasi-elastic part: require some hadrons in detector solid line: inelastic contribution



dashed line: after cuts E

g

is smaller > 10 GeV



E-p z from hadronic state S C He D Need a code, which puts all together to make full calculations need to test analysis strategies to suppress rad. corrections

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 12

and Summary



Djangoh



http://wwwthep.physik.uni mainz.de/~hspiesb/djangoh/djangoh.html

and running

 

is compiled at BNL 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 EIC INT Program, Seattle 2010 - Week 5 13

BACKUP

E.C. Aschenauer EIC INT Program, Seattle 2010 - Week 5 14