role of dynamic geometry in jet tomography
DESCRIPTION
Role of Dynamic Geometry in Jet Tomography. William Horowitz Columbia University December 12, 2005. In conjunction with Simon Wicks, Magdalenda Djordjevic, and Miklos Gyulassy. Motivation. Past tomographic models simplified the calculation by neglecting either: Multigluon fluctuations - PowerPoint PPT PresentationTRANSCRIPT
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Role of Dynamic Geometry in Jet Tomography
William HorowitzColumbia UniversityDecember 12, 2005
In conjunction with Simon Wicks, Magdalenda Djordjevic, and Miklos Gyulassy
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Motivation
• Past tomographic models simplified the calculation by neglecting either:– Multigluon fluctuations– Path length fluctuations
• For fixed-length calculations, reasonable but unjustifiable length L~5 fm used
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Significance of Nuclear Profile
• Simpler densities create a surface biasHard Cylinder Hard Sphere Woods-Saxon
Toy model for purely geometric radiative loss from Drees, Feng, Jia, Phys. Rev. C.71:034909
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Edgy Geometry
• We use the Woods-Saxon nuclear geometry, which has a fuzzy “edge”
• There is no unique, natural LWS definition– Two examples (of many possibilities):
• We will use the latter formula
,)0(
)ˆ( 0
ρ
dllnxρL
ρ
dllnxρL
)ˆ( 0
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Partonic RAA Model
– where P incoherently convolves DGLV energy loss (including multigluon fluctuations) with the infinite-time elastic energy loss for fixed s
)(
);;,(ε,ε1ε);(),;(
2
bN
pbφxLPdbxTxdpbφR
coll
Tn
AA
TAA
Momentum Jacobian as survival probability; see, e.g., Gyulassy, nucl-th/0403032
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Volume Emission of Partons
• fixed pT = 15 GeV, yT = = 0, and s = .3
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Average Lengths of Emission
• Dynamic volume depends on partonic species and pT
– For pT = 5, 10, 15, 20 GeV, s = .3
– <Lg> = 1.74, 1.93, 2.16, 2.41 fm
– <Lu> = 3.83, 4.21, 4.47, 4.62 fm
– <Lc> = 4.65, 4.43, 4.48, 4.50 fm
– <Lb> = 6.17, 5.69, 5.43, 5.29 fm
Heavy Flavor Productions Workshop12/12/05 William Horowitz
The Results
• Electrons • Pions
s = .3
Heavy Flavor Productions Workshop12/12/05 William Horowitz
The Results
• Electrons • Pions
s = .4
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Conclusions
• There are several large effects that must be taken into account in any energy loss model:– Multigluon fluctuations– Path length fluctuations– Collisional energy loss
– Running s
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Future Work
• Find more accurate analytic formulae for collisional loss– Molnár’s parton cascade provides
exact numerical answer
• Simultaneously treat elastic and inelastic energy loss– Find a more natural L?
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Future Work (cont’d)
• Allow s to run– Nonzero lower bound to theoretical
error
• Use even more accurate medium density– Hirano’s CGC-initial condition 3+1 D
evolving hydro background
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Let’s Eat!
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Partonic RAA Model
• Exploit the power law production rate to use the momentum Jacobian to define the probability of escape, (1-)n
– pT, final = pT, initial
– n is simply related to the exponent of the power law
– Assumes a slowly changing power law
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Combining Models
• Find a fixed L that reproduces the dynamical length-generated partonic RAA using proper initial spectra followed by fragmentation into pions and electrons
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Vary s
• We expect a big change since
• Erad ~ s3
• Eelas ~ s2
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Finding Fixed L
• Heavies • Lights
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Heavies alph=.4 BT and TG
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Theoretical Error from Length Uncertainty
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Volume Emission fors = .4
Heavy Flavor Productions Workshop12/12/05 William Horowitz
Volume Emission for s = .4 (cont’d)