cgc and initial conditions for heavy ion collisions kevin dusling · 2019-09-30 · cgc and initial...
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CGC and Initial Conditions for Heavy Ion Collisions
Kevin Dusling
North Carolina State UniversityRaleigh, NC 27695
August 22nd, 2012
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Two particle correlations in p+p collisions
1. Evidence for saturation dynamics (the p+p near-side Ridge)
2. Evidence for BFKL evolution (mini-jet decorrelation)
3. Prospects for p+Pb @ LHC
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Part 1: the p+p near side ridge
More than 200 charged particles!
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Novel structure seen in highest multiplicity events
Central (N>110): Min. Bias:
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The Ridge
1. There is a clear scale in the data
2. It is semi-hard and will be argued to be related to Qs
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Multiplicity the same as in Cu+Cu !
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The proton pre-collisionOur field has a good understanding of the proton wave-function:
15 years of HERA data support this picture:
NLO DGLAP fits: http://mstwpdf.hepforge.org/
NLO-BK:Balitsky, Chirilli PRD 77 014019Kovchegov, Weigert NPA 784 188Albacete, Kovchegov PRD 75 125021
Albacete, Milhano, Quiroga-Arias ,Rojo,arXiv:1203.1043 (2012).Quiroga-Arias, Albacete, Armesto, Milhano, Salgado,J.Phys.G G38 (2011) 124124.Albacete, Armesto, Milhano, Salgado,PRD80 (2009) 034031.
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Power counting in QCD: multiparticle productionLow color charge density (min bias):
High color charge density (central):
Expect enhancement of “Glasma” graph! Is this seen in the data?
Jet graph: Glasma graph:
Jet graph: Glasma graph:
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Forward jet structure
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kT factorization: double gluon production
Gelis, Lappi, Venugopalan, PRD78, 050419 (2008). PRD78, 054020 (2008). PRD79, 094017 (2009).
Dusling, Gelis, Lappi, Venugopalan, NPA 836 159-182 (2010).
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kT factorization: double gluon production
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Angular Structure
Dumitru, Dusling, Gelis, Lalilian-Marion, Lappi, Venugopalan, PLB 697 12-25 (2011).
Condition for Ridge (Qualitatively):
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Forward jet structure
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Ridge in p+p collisions
Dusling, Venugopalan, PRL 108, 262001 (2012).Dumitru, Dusling, Gelis, Jalilian-Marian, Lappi, Venugopalan, PLB 697 12-25 (2011).
Centrality Dependence: Trigger Dependence:
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Role played by transverse flow
Left: No intrinsic correlation in ∆φ followed by radial boost.
Right: Intrinsic azimuthal correlation followed by boost.
Transverse flow increases near side collimation;but is it seen in the data?
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p+p vs A+AIn p+p we are seeing the intrinsic collimation from a single flux tube
Increasing transverse flow in p+p creates a discrepancy with data.
Yet, transverse flow is needed to explain identical measurementsin Pb+Pb
Are we sure the A+A ridge is probing the nuclear wavefunction?Dusling, Venugopalan, PRL 108, 262001 (2012).
In A+A there are many such tubeseach with an intrinsic correlationenhanced by flow
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Heavy-Ion Ridge
The correlation is long range in rapidity.Causality dictates the correlation formed early.
And it persists to the final state:
Dumitru, Gelis, McLerran, Venugopalan,NPA810 (2008) 91-108.Dusling, Gelis, Lappi, Venugopalan,NPA836 (2010) 159-182.Ma, Wang, PRL 106 (2011) 162301.
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Need for EIC:
World collection of small x (x ≤ 0.01) data for DIS on nuclei.
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Part II: Jet Decorrelation
One can look for the growth in cross section with larger rapidity gaps as first suggested by Muller and Navelet.
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Mini jets in kT factorization
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Evidence for BFKL evolution
There is a clear need for evolution between the triggered particles (even for a rapidity gap as small as 2-4 units)
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Part 3: Prospects for p+Pb
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Ridge in p+Pb
Ridge in p+Pb is smaller than in p+p for CMS acceptance.Signal will also have to be pulled from a larger background.
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Summary
● Strong color sources lead to enhancement of QCD diagram responsible for near-side enhancement
● Near side collimation is a clear signature of saturation dynamics
● Clear evidence for BFKL evolution in CMS dijet measurments
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Backup
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High multiplicity are b=0 collisions
Dumitru, Gelis, McLerran, Venugopalan, NPA810 91-108 (2008).Dusling, Fernandez-Fraile, Venugopalan NPA828 (2009) 161-177.Gelis, Lappi, McLerran, NPA828 (2009) 149-160.
Emprical: Tribedy, Venugopalan, NPA850 (2011) 136-156. Lattice (CYM): Lappi, Srednyak, Venugopalan, JHEP01 (2010) 066. Schenke, Tribedy, Venugopalan, arXiv:1206.6805
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p+p pT distribution
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CMS Acceptance
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Gluon radiation
Kuraev, Lipatov, Fadin, Sov.Phys.JETP44 443-450 (1976). Sov.Phys.JETP45 199-204 (1977).
Balitsky, Lipatov, Sov.J.Nucl.Phys 28 822-829 (1978).
As the energy is increased new gluons are emitted with probability
And as long as the density remains low the evolution is linear
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BK Evolution Equation
Balitsky, NPB 463, 99 (1996).Kovchegov, PRD 60, 034008 (1999).
Jalilian-Marian, Kovner, McLerran, Weigert, PRD 55 5414 (1997).Jalilian-Marian, Kovner, Leonidov, Weigert, NPB 504 415 (1997),
PRD 59 014014 (1999).
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NLO BK Equation
Balitsky, Chirilli PRD 77 014019Kovchegov, Weigert NPA 784 188Albacete, Kovchegov PRD 75 125021
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Blast Wave Model
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kT factorization: single gluon production
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BFKL Formalism