Nuclear PDFs. A. Kusina. xfitter Meeting March 2017, St Hilda s College, Oxford, UK

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1 Nuclear PDFs A. Kusina Laboratoire de Physique Subatomique et de Cosmologie (LPSC) 53 Rue des Martyrs Grenoble, France xfitter Meeting March 2017, St Hilda s College, Oxford, UK

2 Motivation Cross-sections in nuclear collisions are modified Anti-shadowing Fermi-motion Shadowing EMC-effect We translate this modifications into universal quantities: nuclear PDFs (npdfs) 1 / 27

3 Available nuclear PDFs Multiplicative nuclear correction factors NEW f p/a i free proton (x N, µ 0 ) = R i (x N, µ 0, A) fi (x N, µ 0 ) HKN: Hirai, Kumano, Nagai [PRC 76, (2007), arxiv: ] DSSZ: de Florian, Sassot, Stratmann, Zurita [PRD 85, (2012), arxiv: ] EPS: Eskola, Paukkunen, Salgado [JHEP 04 (2009) 065, arxiv: ] EPPS16: Eskola, Paakkinen, Paukkunen, Salgado [arxiv: ] Native nuclear PDFs ncteq [PRD 93, (2016), arxiv: ] f p/a i (x N, µ 0 ) = f i (x N, A, µ 0 ) free proton f i (x N, A = 1, µ 0 ) fi (x N, µ 0 ) 2 / 27

4 ncteq npdf framework [PRD 93, (2016), arxiv: ] Parametrization bound proton PDFs xf p/a i (x, Q 0 ) = c 0 x c1 (1 x) c2 e c3x (1 + e c4 x) c5 ( ) c k c k (A) c k,0 + c k,1 1 A c k,2 PDF of nucleus (A - mass, Z - charge) f (A,Z) i (x, Q) = Z A f p/a i (x, Q) + A Z A f n/a i (x, Q) Experimental data DIS (NMC, BCDMS, Hermes, SLAC, E665, EMC) Drell-Yan (E772, E886) 740 data pts. Pion production (PHENIX, STAR) 3 / 27

5 / / ncteq15 fit Fit details χ 2 /dof = 1 QCD@NLO Hessian error PDFs R P b = f P b = f p/a + f P b f P b free-proton f n/a data points ncteq15 =10 GeV EPS09 HKN / 27

6 EPPS16 [arxiv: ] First analysis with ppb LHC data: W ± from CMS Z from CMS and ATLAS dijet from CMS R p/p b = f p/p b (x, Q) f p (x, Q) R u Pb V (x, Q 2 = 10 GeV 2 ) R d Pb (x, Q2 = 10 GeV 2 ) EPPS16 EPPS16 EPPS16 ncteq15 ncteq15 ncteq x x x R d Pb V (x, Q 2 = 10 GeV 2 ) EPPS16 EPPS16 EPPS16 ncteq15 ncteq15 ncteq x x x R s Pb (x, Q 2 = 10 GeV 2 ) R u Pb (x, Q 2 = 10 GeV 2 ) R g Pb (x, Q 2 = 10 GeV 2 ) 5 / 27

7 EPPS16 [arxiv: ] First analysis with ppb LHC data: W ± from CMS Z from CMS and ATLAS dijet from CMS R p/p b = f p/p b (x, Q) f p (x, Q) R V Pb (x, Q 2 = 10 GeV 2 ) R S Pb (x, Q 2 = 10 GeV 2 ) R g Pb (x, Q 2 = 10 GeV 2 ) 1.6 EPPS16 EPS09 DSSZ x 1.6 EPPS16 EPS09 DSSZ x 1.6 EPPS16 EPS09 DSSZ x 5 / 27

8 Differences with the free-proton PDFs Theoretical status of Factorization Parametrization more parameters to model A-dependence Different data sets much less data: Less data less constraining power more assumptions (fixing) about fitting parameters 6 / 27

9 Differences with the free-proton PDFs Theoretical status of Factorization Parametrization more parameters to model A-dependence Different data sets much less data: Less data less constraining power more assumptions (fixing) about fitting parameters 6 / 27

Differences with the free-proton PDFs Theoretical status of Factorization Parametrization more parameters to model A-dependence Different data sets much less data: Q 2 [GeV 2 ] 10 3 10 2 10 1 10 0

10 Differences with the free-proton PDFs Theoretical status of Factorization Parametrization more parameters to model A-dependence Different data sets much less data: Q 2 [GeV 2 ] NMC EMC SLAC BCDMS Hermes FNAL E665 DY: FNAL ncteq15 dataset Non-perturbative x Less data less constraining power more assumptions (fixing) about fitting parameters 6 / 27

11 Nuclear strange and LHC data [arxiv: ] 7 / 27

12 Available ppb LHC data W/Z production Jets ATLAS [arxiv: , ATLAS-CONF ] CMS [arxiv: , arxiv: ] LHCb [arxiv: ] ALICE [arxiv: ] ATLAS [arxiv: ] CMS [arxiv:140433, CMS-PAS-HIN ] Charged particle production (FFs dependence) CMS [CMS-PAS-HIN ] ALICE [arxiv: , arxiv: ] Isolated photons (PbPb) ATLAS [arxiv: ] CMS [arxiv: ] ALICE [arxiv: ] 8 / 27

13 Available ppb LHC data W/Z production Jets ATLAS [arxiv: , ATLAS-CONF ] CMS [arxiv: , arxiv: ] LHCb [arxiv: ] ALICE [arxiv: ] ATLAS [arxiv: ] CMS [arxiv:140433, CMS-PAS-HIN ] Charged particle production (FFs dependence) CMS [CMS-PAS-HIN ] ALICE [arxiv: , arxiv: ] Isolated photons (PbPb) ATLAS [arxiv: ] CMS [arxiv: ] ALICE [arxiv: ] 8 / 27

14 Available ppb LHC data W/Z production ATLAS [arxiv: , ATLAS-CONF ] CMS [arxiv: , arxiv: ] LHCb [arxiv: ] ALICE [arxiv: ] ATLAS LHCb CMS ALICE 1 0 y W ± A W l Z A Z FB A W FB x 2 8 / 27

15 Available ppb LHC data W/Z production ATLAS [arxiv: , ATLAS-CONF ] CMS [arxiv: , arxiv: ] LHCb [arxiv: ] ALICE [arxiv: ] Q 2 [GeV 2 ] NMC EMC SLAC BCDMS Hermes FNAL E665 DY: FNAL LHC W/Z 10 0 Non-perturbative/higher-twist x 7 / 27

16 1 PbPb data dσ σ tot dy Z [ JHEP 03 (2015) 022, ; PRL 110 (2013) , ] [ PLB 715 (2012) 66, ; EPJ C75 (2015) 23, ] dσ dyz σtot R Al R 0.1 CMS Z µµ PbPb, s =2.76 TeV ncteq15 CT y Z CMS PbPb, W char. asym. s = TeV ncteq15 CT y l R Al R ATLAS Z PbPb s = TeV ncteq15 CT yz ATLAS PbPb, W char. asym. s = TeV ncteq15 CT yl 8 / 27

17 1 1 PbPb data dσ σ tot dy Z [ JHEP 03 (2015) 022, ; PRL 110 (2013) , ] [ PLB 715 (2012) 66, ; EPJ C75 (2015) 23, ] dσ dyz σtot R Al 0.1 CMS Z µµ PbPb, s =2.76 TeV ncteq15 CT Comments R ATLAS Z PbPb s = TeV ncteq15 CT Not very sensitive 1.5 to2.0nuclear3 corrections y Z yz Uncertainties too large to bring constraints on npdfs Al R 0.3 CMS PbPb, W char. asym. s = TeV ncteq15 CT y l R 0.3 ATLAS PbPb, W char. asym. s = TeV ncteq15 CT yl 8 / 27

18 ppb data: CMS & ATLAS W ± [PLB 750 (2015) 565, arxiv: ] [ATLAS-CONF ] dσ(w + l + ν)/dyl + [nb] CMS ppb s = TeV ncteq15 Data CT dσ(w l ν)/dyl [nb] CMS ppb s = TeV ncteq15 Data CT R R y l y l dσ(w + l + ν)/dyl + [nb] ATLAS ppb s = TeV ncteq15 Data CT dσ(w l ν)/dyl [nb] ATLAS ppb s = TeV ncteq15 Data CT R R y l y l 9 / 27

19 ppb data: CMS & ATLAS Z [PLB 759 (2016) 36, arxiv: ] [PRC 92 (2015) , arxiv: ] R dσ(z ll)/dyz [nb] CMS ppb s = TeV ncteq15 Data CT y Z dσ(z ll)/dyz [nb] R ATLAS ppb s = TeV ncteq15 Data CT y Z 10 / 27

20 ppb data: LHCb & ALICE W/Z [arxiv: ] [JHEP 09 (2014) 030, arxiv: ] R σ(w + l + ν) [nb] ALICE ppb s = TeV ncteq15 Data CT y l + σ(z ll) [nb] σ(w l ν) [nb] R LHCb ppb s = TeV MSTW2008 Data ncteq15 ALICE ppb s = TeV ncteq15 Data CT y l R y Z 11 / 27

21 ppb data Comments Overall good description of the data Very good for y < 0 where ncteq15 has data. Some leverage in the y > 0 (low x) region mainly extrapolation ALICE and LHCb interesting with more data Potential constraining power from the ATLAS and CMS W + rapidity distributions. In particular where we don t have data at the moment at x shadowing region 12 / 27

22 Strange quark Correlation of W + vs. W cross section with CMS data Strange is fixed in ncteq15 Compare 2- vs. 5-flavour scenario σ(ppb W + l + ν) [nb] ncteq15 CTEQ EPS 2 flavours 5 flavours CT10 + EPS CT σ(ppb W l ν) [nb] data The impact of the strange is 30% Most of the difference between CT10+EPS09 and ncteq15 is the underlying strange contribution in CT10 PDFs Nuclear corrections very close to each other Consistently lower than proton-proton results shadowing sets up too early? 13 / 27

23 Strange quark As we move from y < 0 to y > 0 high-x to low-x (i.e. from well constrained to less constrained region) 2 flavours 5 flavours CMS σ(ppb W + l + ν) [nb] y < 1 ncteq15 CTEQ EPS CT10 + EPS CT10 data σ(ppb W + l + ν) [nb] 240 y < σ(ppb W + l + ν) [nb] 200 y > σ(ppb W l ν) [nb] σ(ppb W l ν) [nb] σ(ppb W l ν) [nb] At y < 0 nuclear corrections > 1 (anti-shadowing) pull results toward data As we move to higher y it seems we are little short shadowing region Hypothetic: small negative s s asymmetry at high-x? 14 / 27

24 What about strange form di-muon data? dσ(w + l + ν)/dyl + [nb] R CMS ppb s = TeV ncteq15 Data CT yl + dσ(w + l + ν)/dy l + [nb] R CMS ppb s =5.02 TeV strall2c ncteq15 CT10 Data y l + 15 / 27

25 Impact on the ncteq15 PDFs: reweighting analysis 16 / 27

26 Reweighting literature Intoruced by Giele and Keller [arxiv:hep-ph/ ] Developed later by NNPDF [arxiv: ] Application and developments for Hessian PDF sets [arxiv: , arxiv: ] 17 / 27

27 Reweighting for Hessian PDFs [arxiv: , arxiv: ] 1. Convert Hessian error PDFs into replicas f k = f 0 + N i f (+) i f ( ) i R ki, 2 2. Calculate weights for each replica w k = e 1 2 χ2 k /T 1, Nrep N rep i e 1 2 χ2 k /T χ2 k = 3. Calculate observables with new (reweighted) PDFs N data j (D j T k j )2 σ 2 j N rep O new = 1 w k O(f k ), N rep k=1 δ O new = 1 N rep w k (O(f k ) O ) 2. N rep k=1 18 / 27

28 Reweighting for Hessian PDFs [arxiv: , arxiv: ] 1. Convert Hessian error PDFs into replicas f k = f 0 + N i f (+) i f ( ) i R ki, 2 2. Calculate weights for each replica w k = e 1 2 χ2 k /T 1, Nrep N rep i e 1 2 χ2 k /T χ2 k = 3. Calculate observables with new (reweighted) PDFs N data To speed up calculations in case of ppb data we can exploit σ k = f p ˆσ [ f Pb 0 + N i f Pb(+) i j (D j T k j )2 σ 2 j f Pb( ) ] i R ki / 27

29 Reweighting with LHC data We used only W/Z production data from ppb collisions ATLAS [arxiv: , ATLAS-CONF ] CMS [arxiv: , arxiv: ] LHCb [arxiv: ] ALICE [arxiv: ] The dominate role is played by the CMS W production data [arxiv: ] 19 / 27

30 χ 2 values for all used data sets χ 2 /N data (N data =102) before : 2.43 after : 1.78 χ 2 before /N data χ 2 after /N data LHCB Z FWD ATLAS WPM ASYM ALICE WM BWD ALICE WP FWD CMS WP ALICE WM FWD ATLAS WM LHCB Z BWD ALICE WP BWD ATLAS WP CMS WPM ASYM CMS Z CMS WM CMS Z AFB CMS WPM RATIO ATLAS Z 20 / 27

31 Reweighting with LHC data CMS & ATLAS W + data before reweighting after reweighting 120 CMS W ATLAS W + R χ 2 /N data before : 5.07 after : CMS W + 50 data 40 before rew. after rew y l + R χ 2 /N data before : 1.31 after : 2 50 ATLAS W + data 40 before rew. after rew y l + 21 / 27

32 Reweighting with LHC data Example reweighted PDFs before reweighting after reweighting u Q =10 GeV, Nrep =10000 before rew. after rew. 0.5 d Q =10 GeV, Nrep =10000 before rew. after rew. 0.5 xu Pb (x) 0.3 x d Pb (x) R x R x 21 / 27

33 Reweighting with LHC data Example reweighted PDFs before reweighting after reweighting g Q =10 GeV, Nrep =10000 before rew. after rew. 0.5 s Q =10 GeV, Nrep =10000 before rew. after rew. 10 xg(x) 8 xs(x) R x R x 21 / 27

34 Caveats of the reweighting analysis R χ 2 /N data before : 5.07 after : CMS W + 50 data 40 before rew. after rew y l + Substantial region (y 0 x < 10 2 ) where ncteq15 PDFs are extrapolated y = 2 x 10 3 earlier data x 10 2 limited flexibility of the PDF parametrization can not simultanously accomodate modifications at positive and negative rapidites strange PDF tied to ū + d distribution 22 / 27

35 LHC jet data from EPPS16 [arxiv: ] First analysis with ppb LHC data: W ± from CMS Z from CMS and ATLAS dijet from CMS dσ(η 65)/dσ( η 65) EPPS16 ncteq15 DSSZ dijets ppb s = 5.02 TeV p leading T > 120 GeV CMS data p subleading T > 30 GeV ηlab jet < 3.0 dσ(y l +)/dσ( y l +) CMS data No nuclear effects EPPS16 W + production, ppb s = 5.02 TeV p T (l + ) > 25 GeV dσ(y l )/dσ( y l ) CMS data No nuclear effects EPPS16 W production, ppb, s = 5.02 TeV p T (l ) > 25 GeV η 65 lepton rapidity (lab frame) lepton rapidity (lab frame) 23 / 27

36 Summary 24 / 27

37 Summary LHC ppb data important for npdfs: gluon PDF strange PDF delayed shadowing? which could be compatible with what is indicated by the NuTeV neutrino DIS data possible nuclear strange asymmetry Current LHC ppb data are still limited in precision, however, more data with higher statistics have been collected in Dec Full fit with these new data will be performed when the data will become available allows to remove assumptions (open new parameters, e.g. gluon, strange) constraints on previously fixed distributions (hard to estimate impact via reweighting) stabilizes fits makes errors estimates more reliable 25 / 27

38 Summary More LHC data for different hard processes will allow for lead-only fit and also for further tests of uniersality of npdfs. Data for coloured and un-coloured final states to test shadowing vs energy loss effects. 26 / 27

39 Thank You

40 BACKUP SLIDES 28 / 27

41 Strange and free-proton baseline dσ/dy [nb] W + LHC 14 ud LHC 14 TeV cs cd us y [PRD85 (2012) , arxiv: ] dσ/dy [nb] W + Tevatron ud Tevartron cs cd us y Strange constributions at the LHC are much more important than in previous experiments. We should look more carefully at nuclear strange. open strange degrees of freedom use newer free-proton baseline with LHC data 29 / 27

42 EPS study of LHC data impact Used data: W/Z boson production from ppb collisions most importantly: CMS W production [arxiv: ] Jets & dijets CMS dijets look promising [arxiv:140433] Charged-particle production Biggest impact comes from dijet data modifying gluon distribution s [EPJC (2016), 76:218, arxiv: ] [arxiv: ] R G reweighted R G (EPS & CT) old R G (EPS & CT) [arxiv: ] x / 27

43 EPPS16 [arxiv: ] First analysis with ppb LHC data: W ± from CMS Z from CMS and ATLAS dijet from CMS R u Pb V (x, Q 2 = 10 GeV 2 ) R d Pb (x, Q2 = 10 GeV 2 ) EPPS16 EPPS16 EPPS16 ncteq15 ncteq15 ncteq x x x R d Pb V (x, Q 2 = 10 GeV 2 ) EPPS16 EPPS16 EPPS16 ncteq15 ncteq15 ncteq x x x R s Pb (x, Q 2 = 10 GeV 2 ) R u Pb (x, Q 2 = 10 GeV 2 ) R g Pb (x, Q 2 = 10 GeV 2 ) 31 / 27

44 EPPS16 [arxiv: ] First analysis with ppb LHC data: W ± from CMS Z from CMS and ATLAS dijet from CMS dσ(η 65)/dσ( η 65) EPPS16 ncteq15 DSSZ dijets ppb s = 5.02 TeV p leading T > 120 GeV CMS data p subleading T > 30 GeV ηlab jet < 3.0 dσ(y l +)/dσ( y l +) CMS data No nuclear effects EPPS16 W + production, ppb s = 5.02 TeV p T (l + ) > 25 GeV dσ(y l )/dσ( y l ) CMS data No nuclear effects EPPS16 W production, ppb, s = 5.02 TeV p T (l ) > 25 GeV η 65 lepton rapidity (lab frame) lepton rapidity (lab frame) 31 / 27

45 CT10 vs. CTEQ6.1 PDFs Q =10 GeV Q =10 GeV xu(x) xd(x) xu(x) xd(x) CTEQ6.1 CT x CTEQ6.1 CT x CTEQ6.1 CT x CTEQ6.1 CT x xs(x) xū(x) CTEQ CT x CTEQ CT x xg(x) x d(x) CTEQ CT x CTEQ6.1 2 CT x xs(x) xū(x) CTEQ6.1 CT x CTEQ6.1 CT x xg(x) x d(x) CTEQ6.1 CT x CTEQ6.1 CT x 32 / 27

46 Importance of free-proton baseline CMS W + data [arxiv: ] 120 full result quark family (no s, c, b) dσ(w + l + ν)/dy l + [nb] CMS ppb s =5.02 TeV ncteq15 CT10 +EPS09 CT10 CTEQ6.1 +EPS09 Data dσ(w + l + ν)/dy l + [nb] CMS ppb s =5.02 TeV ncteq15 CT10 +EPS09 CT10 CTEQ6.1 +EPS09 Data R R y l y l + 33 / 27

47 What about strange form di-muon data? dσ(w + l + ν)/dyl + [nb] R CMS ppb s = TeV ncteq15 Data CT yl + dσ(w + l + ν)/dy l + [nb] R CMS ppb s =5.02 TeV strall2c ncteq15 CT10 Data y l + xs(x) CT10 Pb ncteq15 Pb 0.1 strall2c Pb x xū(x) Q =10 GeV CT10 Pb ncteq15 Pb 0.1 strall2c Pb x 34 / 27

48 Kinematic reach of LHC W ± /Z data x TeV S = 8TeV y = 4 y = TeV y = 2 y = 1 y = 0 y = 1 y = 2 y = 3 y = x 1 Z W ± Z W ± Z W ± y W ± A W l Z A Z FB ATLAS LHCb CMS ALICE AFB W x 2 35 / 27

49 Kinematic reach of data DIS and DY: π 0 production: Q 2 [GeV 2 ] NMC EMC SLAC BCDMS Hermes FNAL E665 DY: FNAL =. =. % % % % 10 0 % = % x x % 36 / 27

50 Reweighting with LHC data ATLAS W ± data [ATLAS-CONF ] before reweighting after reweighting 110 W + 90 W 100 χ 2 /N data before : 1.31 after : 2 80 χ 2 /N data before : 1.17 after : R ATLAS W + data 40 before rew. after rew y l + R 50 ATLAS W data 40 before rew. after rew y l 37 / 27

51 Reweighting with LHC data CMS charge lepton (A l ) and forward-backward (A FB ) asymmetries for W ± [arxiv: ] before reweighting after reweighting 0.3 A l 1.6 A FB 0.1 χ 2 /Ndata before : after : χ 2 /Ndata before : after : CMS AFB data before rew. after rew. 1.1 R 0.1 CMS Al data before rew. after rew y l R y l 37 / 27

52 ncteq15 fit Fit details χ 2 /dof = 1 QCD@NLO Hessian error PDFs 740 data points DIS DIS & DY DIS DIS & DY 8 DIS DY DIS DY DIS π 0 χ 2 /dof He/D Li/D Be/D C/D N/D Al/D Ca/D Fe/D Cu/D Kr/D Ag/D Sn/D Xe/D W/D Au/D Pb/D C/Li Ca/Li Fe/Be W/Be Be/C Al/C Ca/C Fe/C Sn/C Pb/C DAu/pp 38 / 27

53 / / ncteq15 fit Fit details χ 2 /dof = 1 QCD@NLO Hessian error PDFs 740 data points ncteq15 =10 GeV EPS09 HKN / 27

54 ncteq results Nuclear PDFs A-dependence (Q = 10GeV) xf A i (x, Q) xf p/a xf p/a xf p/a xf p/a g x 0.5 u v x u x ū xf p/a xf p/a xf p/a xf p/a s A=1 A=4 A=9 A= A=27 A=40 A=56 A= A=119 A=131 A=197 A= x d v x d x d / 27

55 ncteq results Nuclear correction factors (Q = 10 GeV) ncteq HKN07 EPS09 DSSZ R i (P b) = f p/p b i (x, Q) (x, Q) f p i different solution for d-valence & u-valence compared to EPS09 & DSSZ sea quark nuclear correction factors similar to EPS09 nuclear correction factors depend largely on underlying proton baseline 40 / 27

56 / / / / Tolerance criteria (, ) T=70 T=50 T=35 T=10 T= =1.3 GeV (, ) xf p/p b i (x, Q = 1.3GeV) (, ) (, ) / 27

57 / / Nuclear lead PDFs (f A = Z A f p/a + A Z A f n/a ) (, ) (, ) ncteq15 EPS09 HKN07 =10 GeV ncteq15 =10 GeV EPS09 HKN / 27

58 Variables: DIS of nuclear target ea e X DIS variables { in case on nucleons Q 2 q 2 e q e in nucleus x A Q2 2 p A q A X p A nucleus momentum x A (0, 1) analog of Bjorken variable (fraction of the nucleus momentum carried by a nucleon) Analogue variables for partons: pn = p A A average nucleon momentum xn Q2 2 p N q = A x A parton momentum fraction with respect to the avarage nucleon momentum p N x N (0, A) parton can carry more than the average nucleon momentum p N. 43 / 27

59 ncteq results: F 2 ratios Structure function ratio R = F 2 F e (x, Q) F2 D (x, Q) good data description despite different u-valence & d-valence ratios are similar to EPS09 F 2 Fe /F 2 D F 2 Fe /F 2 D Q 2 = 5 GeV 2 ncteq15 HKN07 EPS x Q 2 = 20 GeV 2 ncteq15 HKN07 EPS x 44 / 27

60 Description of fitted data: F 2 ratios 1.1 / npts=9 = npts=27 = npts=3 = npts=15 =13 He/D NMC(95) SLAC-E139(94) BCDMS(95) N/D Cu/D EMC(88) EMC-ADD(93) EMC-CAR(93) Au/D SLAC-E139(94) R = F A 2 (x,q) F D 2 (x,q) npts=11 =6.1 npts=3 =1.14 npts=2 =1.59 NMC(95) Li/D Al/D SLAC-E139(94) Ag/D SLAC-E139(94) npts=3 1 Pb/D = FNAL-E665(95) npts=3 =1.37 npts=17 =14.12 npts=8 =17.2 Be/D SLAC-E139(94) Ca/D NMC(95) FNAL-E665(95) SLAC-E139(94) EMC(88) Sn/D npts=38 =31.9 npts=24 =16.87 npts=2 =2 C/D EMC(88) NMC(95) FNAL-E665(95) SLAC-E139(94) Fe/D BCDMS(85) BCDMS(88) SLAC-E049(83) SLAC-E139(94) Xe/D SLAC-E139(94) / 1.1 NMC(96) npts=14 = NMC(96) npts=14 =4.1 Pb/C Be/C R = F A 2 (x,q) F A 2 (x,q) npts=14 =5.38 NMC(96) npts=7 =5.55 NMC(95) Al/C C/Li npts=21 =9.76 NMC(96) NMC(95) Ca/C npts=14 =9.79 NMC(96) Fe/C Ca/Li npts=7 =1.12 NMC(95) 45 / 27

61 Description of fitted data: F 2 ratios for Sn/C 1.1 / NMC(96) npts=111 =64.41 x= 125 NMC(96) x= 175 NMC(96) x= x= x= x= [ ] [ ] [ ] NMC(96) NMC(96) NMC(96) 1 10 x= x= x= [ ] [ ] [ ] NMC(96) NMC(96) NMC(96) 1 10 x= x= x= [ ] [ ] [ ] NMC(96) NMC(96) NMC(96) 1 10 x= x= x= 1.1 [ ] [ ] [ ] NMC(96) NMC(96) NMC(96) [ ] [ ] [ ] 46 / 27

62 Description of fitted data: σ DY ratios R = σa DY (x,q) σ D DY (x,q) R = σa DY (x,q) σ A DY (x,q) / 1.1 npts=9 =7.93 C/D npts=9 =2.72 Ca/D / Fe/Be npts=28 =23.1 Fe/Be Fe/Be Fe/Be FNAL-E772 FNAL-E GeV FNAL-E866(99) 5.5 GeV FNAL-E866(99) 6.5 GeV FNAL-E866(99) 7.5 GeV FNAL-E866(99) npts=9 =3.17 Fe/D npts=9 = W/D 1 5 npts=280.5 W/Be 5 1 = W/Be W/Be W/Be FNAL-E772 FNAL-E GeV FNAL-E866(99) 5.5 GeV FNAL-E866(99) 6.5 GeV FNAL-E866(99) 7.5 GeV FNAL-E866(99) / 27

63 [ N. Armesto, 2015 LHeC Workshop, Chavannes-de-Bogis, June 26th 2015]

64 [ N. Armesto, 2015 LHeC Workshop, Chavannes-de-Bogis, June 26th 2015]

65 [ N. Armesto, 2015 LHeC Workshop, Chavannes-de-Bogis, June 26th 2015]

66 EPS09 framework [JHEP 04 (2009) 065, arxiv: ] LO & NLO PDFs with errors Error PDFs produced with Hessian method Parametrization (Q 0=1.3GeV) f p/a i (x N, µ 0) = R i(x N, µ 0, A, Z) f i(x N, µ 0), i = valence, sea, g a 0 + (a 1 + a 2x)(e x e xa ) x x a R i(x, A, Z) = b 0 + b 1x + b 2x 2 + b 3x 3 x a x x e c 0 + (c 1 c 2x)(1 x) β x e x 1 A-dependence of fitting parameters (d i = a i, b i, ) y ( a d A i = d A ref i CTEQ6.1M free proton baseline Neglects x N > 1 Data: DIS, DY, π RHIC ) pdi A A ref y 0 shadowing antishadowing x a EMCeffect Fermimotion x e y e 51 / 27

67 Motivations: proton Strange PDF Before CTEQ6.6 proton PDFs it was assumed P. Nadolsky et al. PRD 78, (2008), arxiv: s(x) = s(x) κ ū(x) + d(x), κ = Underestimating s PDF uncertainty, as ū, d are much better constrained. Neutrino-nucleon dimuon data (CCFR, NuTeV) s i (x) CTEQ6.6 s 0 (x) allowed to fit s PDF independently of ū, d sea. CTEQ x 52 / 27

68 ATLAS strange measurement ATLAS has used W/Z production to infer constraints on the strange quark distribution (2010 data, 35pb 1 ) G. Aad et al. (ATLAS Collaboration) Phys. Rev. Lett. 109, (2012), arxiv: for Q 2 = 1.9 GeV 2 and x = 23: r s = 0.5(s + s)/ d = / 27

69 CMS W c final states measurement CMS measured ratios of cross-sections using 36pb 1 of data CMS-PAS-EWK arxiv: R ± c = σ(w + c) σ(w = 2 ± 0.19(stat.) ± 4(sys.) c) see also: W. J. Stirling, E. Vryonidou, Phys. Rev. Lett. 109, (2012), arxiv: / 27

Nuclear PDFs: latest update

Nuclear PDFs: latest update (and future facilities) P. Zurita February 16th, 2017 Wright laboratory, Yale University, CT, USA Disclaimer I will talk only about observables included in PDFs and npdfs fits,