Nuclear PDFs at the LHC and beyond Carlos A. Salgado Universidade - - PowerPoint PPT Presentation
Nuclear PDFs at the LHC and beyond Carlos A. Salgado Universidade de Santiago de Compostela Nuclei at the FHC CERN - December - 2013 @CASSalgado @HotLHC Disclaimer Very little time to prepare this talk: Slides mostly taken from other
Nuclear PDFs at the LHC and beyond
Nuclei at the FHC CERN - December - 2013
Carlos A. Salgado Universidade de Santiago de Compostela
@CASSalgado @HotLHC
2
Disclaimer Very little time to prepare this talk: Slides mostly taken from other (older) talks and/or stolen from other people [especially Pia Zurita and Hannu Paukkunen - they’ve agreed, so thanks :)] [I hope this is good enough for this first informal meeting]
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY LHeC 50(e)+2750(Pb) p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY LHeC 50(e)+2750(Pb) p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
New regions never explored in HIC small-x and large-Q
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY LHeC 50(e)+2750(Pb) p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
Constrain PDFs Check expected saturated region
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
3
Kinematical reach in nuclear collisions
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
A
x
10
10
10
10
10
10
10 1 )
2
(GeV
2
Q 1 10
2
10
3
10
4
10
5
10
6
10
7
10
8
10 (x)
2 sat,Pb
Q Present DIS+DY LHeC 50(e)+2750(Pb) p+Pb @ LHC (7 TeV+2.75 TeV) Present nuclear DIS and Drell-Yan in p+A d+Au @ RHIC 0 < y < 3.2
= 6.6
laby = 6
l a by = 4
l a by = 2
l a by =
l a by
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Assuming 50+20 FHC
xFCC ∼ xLHC e−2
4
Why proton-nucleus?
The proton structure is constrained by DIS + other data HERA data of utmost importance Need pA to study the high-energy nuclear structure DIS data is old (90’s) short number and with limited range pA@LHC is the only experimental condition available before an eventual lepton-A collider (LHeC, eRHIC?) Needed as benchmark for the AA program High-density effects (saturation) enhanced in nuclei
[To study the structure of a large object make collisions with smaller objects (Rutherford experiment...)]
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
5
Main goals Check the factorization of nPDFs for hard processes Fix the benchmark for HI hot matter or saturation
nPDFs: global analyses. Status
EKS98 [Eskola, Kolhinen, Ruuskanen, Salgado 1998] HKM [Hirai, Kumano, Miyama, 2001] nDS [de Florian, Sassot, 2003]
HKN [Hirai, Kumano, Nagai, 2004; 2007] EPS08, EPS09 [Eskola, Paukkunen, Salgado, 2008; 2009] Also FGS [2004-2010]; Kovarik et al. [2011]
QM, Annecy, May 2011 pA physics potential at the TeV
A x Stolen from Hannu Paukkunen at JLab Oct 2013
6
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
HKN07
EPS09 DSSZ nCTEQ prelim. Ref.
(2007) 065207 JHEP 0904 (2009) 065 Phys.Rev. D85 (2012) 074028 arXiv:1307.3454
Order
LO & NLO LO & NLO NLO NLO
Neutral current e+A / e+d DIS
√ √ √ √
Drell-Yan dileptons in p+A / p+d
√ √ √ √
RHIC pions in d+Au / p+p
√ √
Neutrino-nucleus DIS
√
Q2 cut in DIS 1GeV 1.3GeV 1GeV 2GeV # of data points 1241 929 1579 708 Free parameters 12 15 25 17 Error sets available
√ √ √
Error tolerance Δχ2
13.7 50 30 35
Baseline
MRST98 CTEQ6.1 MSTW2008 CTEQ6M
Heavy quark treatment
ZM_VFNS ZM_VFNS GM_VFNS GM_VFNS
The contemporary NLO nPDF fits
7
How?: follow free proton approach
Cross sections computed in collinear factorization Define Using a known set for free protons (CTEQ, MRST....) and DGLAP evolution of the nuclear and free proton PDFs Find the minimum of χ2
RA
i (x, Q2) = f A i (x, Q2)
f p
i (x, Q2)
i (x, {ai})
⇥ at Q2
i (x, Q2)
⇥ for {ai}
Compute χ2 [{ai}] Minimum? DGLAP Compute observables at vary (fulfilling sum rules) YES NO
{ai} (x, Q2)
Final answer
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
8
Approximate ranges and constrains in EPS09
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2
Valence Sea quarks Gluons
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
8
Approximate ranges and constrains in EPS09
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2
Valence Sea quarks Gluons
Constrained by DIS
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
8
Approximate ranges and constrains in EPS09
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2
Valence Sea quarks Gluons
Constrained by DIS Constrained by DY
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
8
Approximate ranges and constrains in EPS09
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2
Valence Sea quarks Gluons
Constrained by DIS Constrained by DY Sum rules and dAu@RHIC
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
8
Approximate ranges and constrains in EPS09
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2
Valence Sea quarks Gluons
Constrained by DIS Constrained by DY Sum rules and dAu@RHIC Unconstrained
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
8
Approximate ranges and constrains in EPS09
0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 10-4 10-3 10-2 10-1 1
RA
G(x, Q2)x A = 208 Q2
0 = 2.25 GeV2
Valence Sea quarks Gluons
Constrained by DIS Constrained by DY Sum rules and dAu@RHIC Unconstrained
[these ranges are very approximative... but valid in general for other analyses]
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Comparison
9
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Plots Stolen from Hannu
Sea and valence quarks are similar (except at large-x) Gluons different -- unconstrained + different assumptions and sets of data
10
nCTEQ is special
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Q²=100GeV²
Q²=100GeV² Q²=100GeV² Q²=100GeV²
Q²=100GeV²
Plots Stolen from Hannu
But these results are preliminary, only shown in conferences, not published
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
An excellent agreement with e.g. CTEQ6.6+EPS09 nuclear PDFs A novel PDF re-weighting (not the NNPDF
the compatibilty No reason to believe that the factorization would be violated. Without the normalization the result
NuTeV data). With the normalization, OK Points to an underestimation of the experimental errors (NuTeV)
Neutrinos: Paukkunen & Salgado
Phys.Rev.Lett. 110 (2013) 212301
Stolen from Hannu
11
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
An excellent agreement with e.g. CTEQ6.6+EPS09 nuclear PDFs A novel PDF re-weighting (not the NNPDF
the compatibilty No reason to believe that the factorization would be violated. Without the normalization the result
NuTeV data). With the normalization, OK Points to an underestimation of the experimental errors (NuTeV)
Neutrinos: Paukkunen & Salgado
Phys.Rev.Lett. 110 (2013) 212301
Stolen from Hannu
DSSZ
11
R
0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 ) π Shadowing, EPS09s ( LO pQCD + cold nuclear matter(GeV/c)
Tp
2 4 6 8 10 12 14 16 18 20 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 HIJING 2.1 =0.28 g s =0.28 g DHC, s DHC, no shad. DHC, no shad., indep. frag.Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Inclusive particle at high-pt
Reasonable description, but baryons are not well described by FF Mesons needed - notice disagreement in proton-proton data CMS data needs to be understood - enhancement not possible within nPDFs
[GeV/c]
T
p
1 10
210
|<1)
CM
η (|
pPb
R
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
= 5.02 TeV, charged particles NN s pPb=6.9
collN CMS Preliminary
12
13
W/Z bosons in pA: a very promising tool
0.0 0.05 0.1 0.15 0.2 0.25 0.3 0.0 0.05 0.1 0.15 0.2 0.25 0.3Z-Spectrum, pPb at = 8.8TeV, M=MZ d
2 /dM 2dyR[pb/GeV
2]√s
Comparison with present (PbPb) data good, but not very much sensitivity New data from the pPb run should provide more constraints
Rapidity
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
dN/dy
10 20 30 40 50 60
CMS POWHEG + PYTHIA 6.4 Paukkunen et al., CT10+isospin Paukkunen et al., idem+EPS09 Neufeld et al., MSTW+isospin Neufeld et al., idem+eloss
b)
= 2.76 TeV NN s atx10
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Comparison to the NLO calculations – the gluon PDFs make a difference!
Doga Gulhan, IS2013, Spain
A striking agreement with CT10+EPS09!
The CMS dijets in p+Pb
Eskola, Paukkunen, Salgado, arXiv:1308.6733 Preliminary CMS data “by eye”
Stolen from Hannu
14
15
Checks of factorization: forward@RHIC
10-7 10-6 10-5 10-4 10-3 10-2 10-1 1
Ed
3N/d 3p [GeV
CTEQ6.1M PDFs fDSS FFs
inelastic = 40mb fac= frag= ren=pT2.0 4.0
[GeV]
0.5 1.0 1.5 2.0
Data/Theory
2.0 4.0
[GeV]
BRAHMS pp = 2.2 = 3.2
NLO PQCDInclusive h- 2.0 4.0 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1
Ed
3N/d 3p [GeV
EPS09NLO nPDFs fDSS FFs
inelastic = 40mb2.0 4.0
<Ncoll> = 7.2
fac= frag= ren=pT2.0 4.0
[GeV]
0.5 1.0 1.5 2.0
Data/Theory
2.0 4.0
[GeV]
BRAHMS dAu = 2.2 = 3.2
NLO PQCD h-Inclusive h-
Good description except for pp @ y=3.2 Notice that only yields are provided: need to use Glauber
[Eskola, Paukkunen, Salgado, 2010]
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
15
Checks of factorization: forward@RHIC
10-7 10-6 10-5 10-4 10-3 10-2 10-1 1
Ed
3N/d 3p [GeV
CTEQ6.1M PDFs fDSS FFs
inelastic = 40mb fac= frag= ren=pT2.0 4.0
[GeV]
0.5 1.0 1.5 2.0
Data/Theory
2.0 4.0
[GeV]
BRAHMS pp = 2.2 = 3.2
NLO PQCDInclusive h- 2.0 4.0 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1
Ed
3N/d 3p [GeV
EPS09NLO nPDFs fDSS FFs
inelastic = 40mb2.0 4.0
<Ncoll> = 7.2
fac= frag= ren=pT2.0 4.0
[GeV]
0.5 1.0 1.5 2.0
Data/Theory
2.0 4.0
[GeV]
BRAHMS dAu = 2.2 = 3.2
NLO PQCD h-Inclusive h-
Good description except for pp @ y=3.2 Notice that only yields are provided: need to use Glauber
1 2 3 4 5 6
[GeV]
0.4 0.6 0.8 1.0 1.2
= 2.2
1 2 3 4 5 6
[GeV]
0.4 0.6 0.8 1.0 1.2
= 3.2 BRAHMS h- EPS09NLO
dAu
Ratios not well described
[Eskola, Paukkunen, Salgado, 2010]
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
16
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Summary of comparison with LHC Good compatibility so far with limited sensitivity (except, perhaps CMS dijets) Still waiting for final pPb results...
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
JHEP 1311 (2013) 015
This part stolen from Pia Zurita - Nantes Dec 2013
17
Idea: Study compatibility without a new global fit
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Developed:
(2011) 112 [Erratum-ibid. B 854 (2012) 926] [Erratum-ibid. B 855 (2012) 927].
Guffanti, N. P. Hartland and J. I. Latorre et al. [NNPDF Collaboration], Nucl. Phys. B 855 (2012) 608.
Extended:
Other:
212301 (2013).
18
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
n new points ⇒ For any
After the re-weighting each replica has a different importance O⇥ = 1 Nrep
Nrep
O[fk] Pnew(f) = NχP(χ|f)Pold(f) wk = (χ2
k)
1 2 (n−1)e−χ2 k/2
1 Nrep
Nrep
k=1 (χ2 k)
1 2 (n−1)e−χ2 k/2
O⇥new = 1 Nrep
Nrep
wkO[fk]
19
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
n new points ⇒ For any
After the re-weighting each replica has a different importance O⇥ = 1 Nrep
Nrep
O[fk] Pnew(f) = NχP(χ|f)Pold(f) wk = (χ2
k)
1 2 (n−1)e−χ2 k/2
1 Nrep
Nrep
k=1 (χ2 k)
1 2 (n−1)e−χ2 k/2
O⇥new = 1 Nrep
Nrep
wkO[fk] To quantify the accuracy
NEW FIT RE-Weighting
Neff ≡ exp
⇤ 1 Nrep
Nrep
⌥
k=1
wk log(Nrep/wk) ⇥ ⌃ ⌅
19
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
n=25 χ2 / n < χ2 > / n Neff Before 1.11 1.75
0.84 1.02 624
DGLAP for η=0
20
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
No change in the valence
change in the sea
η = 0 DGLAP
21
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
n=25 χ2 / n < χ2 > / n Neff Before 2.25 2.76
1.50 1.58 229
CGC for η=0
22
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
change in the valence
no change in the sea CGC η = 0
23
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
DGLAP for η=2
No change in the valence Slight modification for the sea
gluon!
24
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
CGC for η=2
the re-weighting method is invalidated n=25 χ2 / n < χ2 > / n Neff Before 36.43 38.62
1.85 1.85
1
25
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
CGC for η=2
the re-weighting method is invalidated n=25 χ2 / n < χ2 > / n Neff Before 36.43 38.62
1.85 1.85
1
25
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
LHeC
26
Summary
Nuclear PDF analyses still taking off at the LHC Present fits are ok New constraints possible, but eventually smaller error bars needed PDF analyses are precision...
27
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
Do we need to go to higher energies?
[first thoughts...]
28
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
We gain a factor of 7 in CM energy - 2 units of rapidity Questions in the last couple of years [my bias...] Jets in QCD matter - role of coherence (color matters, e.g. singlet) Initial stages and thermalization - CQC (factor 1.8 in Qsat) More precision needed - explore smaller times! higher luminosity + higher energy (new observables) small systems - proton-nucleus Explore also new observables: tiny coupling of EW with medium?
29
A new picture of jet quenching
#HP2013Conf - Stellenbosch - Nov. 2013 Jet Physics Theory The parton shower is composed of un-modified subjets (vacuum-like) With a typical radius given by the medium scale For medium-induced radiation each subject is one single emitter Also, 1st calculation of 1->3 splitting performed in SCET and 1st order in opacity expansion [Fickinger, Ovanesyan, Vitev]
Requires more luminosity and/or more energy Typical luminosity of pPb run ~ 0.1 pb-1 ~10 times more at FHC - others, as Higgs (x20) or top (x50), have even larger enhancements
[Estimates made in the plane with MCFM - need to be checked...]
Nuclei at FHC - CERN - Dec 2013 nPDFs etc
More precise observables
30
[Fickinger, Ovanesyan, Vitev]