Nuclear PDFs: latest update

Transcription

1 Nuclear PDFs: latest update (and future facilities) P. Zurita February 16th, 2017 Wright laboratory, Yale University, CT, USA

2 Disclaimer I will talk only about observables included in PDFs and npdfs fits, computed with dear old pqcd. Any other measurement can eventually be included, just not part of the talk :)

3 Outline The questions: what, why, how? Where were we? Where are we? Where are we going? Summary

4 WHAT? What are PDFs? d (p + l! l 0 + X) = X a dˆla!l 0 X f a d (p + l! l 0 + X + h) = X a,b dˆla!b f a D h b d (p + p! l++l ) = X a,b dˆab!l l f a f b d (p + p! X + h) = X a,b,c dˆab!c f a f b D h c

5 WHAT? What are PDFs? d (p + l! l 0 + X) = X a dˆla!l 0 X f a d (p + l! l 0 + X + h) = X a,b dˆla!b f a D h b d (p + p! l++l ) = X a,b dˆab!l l f a f b d (p + p! X + h) = X a,b,c dˆab!c f a f b D h c hard

6 WHAT? What are PDFs? d (p + l! l 0 + X) = X a dˆla!l 0 X f a d (p + l! l 0 + X + h) = X a,b dˆla!b f a D h b d (p + p! l++l ) = X a,b dˆab!l l f a f b d (p + p! X + h) = X a,b,c dˆab!c f a f b D h c SOFT

7 WHAT? But the title reads nuclear PDFs

8 WHAT? But the title reads nuclear PDFs early 80 s: measurement of DIS crosssections in e-a collisions d 2 eh!ex dxdq 2 = 4 2 e.m. xq 4 " 1 y + y2 2! F 2 (x, Q 2 ) y 2 2 F L(x, Q 2 ) #

9 WHAT?

10 WHAT? effect in cross-section is this a hard, soft or hard and soft effect?

11 WHAT? pqcd is successful don t want to throw it away the proposal is: factorization holds change only in the soft part

12 WHAT? so now d (A + l! l 0 + X) = X a dˆla!l 0 X f A a d (A + l! l 0 + X + h) = X a,b dˆla!b f A a D h b d (A + p! l++l ) = X a,b dˆab!l l f A a f b d (A + p! X + h) = X a,b,c dˆab!c f A a f b D h c

13 WHY? do I need these? really? WHY?

14 WHY? do I need these? really? WHY? because in QCD they are crucial for describing the perturbative regime of

15 WHY? do I need these? really? WHY? because in QCD they are crucial for describing the perturbative regime of nuclear DIS

16 WHY? do I need these? really? WHY? because in QCD they are crucial for describing the perturbative regime of nuclear DIS non QGP effects in p-a, d-a, A-A

17 WHY? do I need these? really? WHY? because in QCD they are crucial for describing the perturbative regime of nuclear DIS non QGP effects in p-a, d-a, A-A cosmic rays

18 WHY? do I need these? really? WHY? because in QCD they are crucial for describing the perturbative regime of nuclear DIS non QGP effects in p-a, d-a, A-A cosmic rays neutrino DIS (needed for proton PDFs)

19 HOW? How? All soft contributions are determined by global QCD analyses

20 HOW? How? All soft contributions are determined by global QCD analyses pick data sets

21 HOW? How? All soft contributions are determined by global QCD analyses pick data sets compute the observables

22 HOW? assumed initial shape of the nuclear/proton PDF ratio (R valence, R sea and R gluon ) 1.5 y a antishadowing Fermimotion y 0 shadowing EMCeffect y e 0.2 x a x e f p/a i (x, Q 0 )=f p i (x, Q 0)R i (x, A) A-dependent parameters

23 HOW? How? All soft contributions are determined by global QCD analyses pick data sets compute the observables construct 2 2 X 2= = i w i d exp i i d i th! 2 weights: amount and accuracy of the data data sets: DIS, DY, p(d)-a, SIDIS, cross-sections, rates theory: LO, NLO, quarks mass error treatment: correlation matrix

24 HOW? How? All soft contributions are determined by global QCD analyses pick data sets compute the observables construct 2 2 X 2= = i w i d exp i i d i th! 2 weights: amount and accuracy of the data data sets: DIS, DY, p(d)-a, SIDIS, cross-sections, rates theory: LO, NLO, quarks mass error treatment: correlation matrix move parameters until minimum reached

25 HOW? How? All soft contributions are determined by global QCD analyses pick data sets compute the observables construct 2 2 X 2= = i w i d exp i i d i th! 2 weights: amount and accuracy of the data data sets: DIS, DY, p(d)-a, SIDIS, cross-sections, rates theory: LO, NLO, quarks mass error treatment: correlation matrix move parameters until minimum reached all done!

26 HOW? too good to be true

27 HOW? too good to be true which data sets? to which order? heavy quarks mass effects? scales? error treatment? weights? parameters??

28 WHERE WERE WE? LO EKS: Eskola, Kolhinen, Salgado, Eur.Phys.J. C9 (1999) HKM: Hirai, Kumano, Miyama, Phys.Rev. D64 (2001) nds: de Florian, Sassot, Phys.Rev. D69 (2004) HKN: Hirai, Kumano, Nagai, Phys.Rev. C76 (2007) > KEK nuclear physics textbook (2015) NLO EPS09: Eskola, Paukkunen, Salgado, JHEP 0904 (2009) DSSZ: de Florian, Sassot, Stratmann, PZ, Phys.Rev. D85 (2012) ncteq15: Kovarik et al., Phys.Rev. D93 (2016) EPPS16: Eskola, Paakkinen, Paukkunen, Salgado, arxiv: NNLO KA15: Khanpour, Tehrani, Phys.Rev. D93 (2016) no.1, to come a) A-Z: NNLO b) NNPDF: Pb npdfs

29 WHERE WERE WE? Paukkunen, Nucl. Phys. A 926 (2014) 24

30 WHERE WERE WE? de Florian, Sassot, Stratmann, PZ, Phys.Rev. D85 (2012) d dau /d pp PHENIX STAR most gluon sensitive data d dau /d pp this fit (nff) this fit (DSS) (62 points) d dau /d pp EPS 09 (DSS) nds (DSS) p T [GeV]

31 WHERE WERE WE? Paukkunen, Nucl. Phys. A 926 (2014) 24 Outside the kinematical region probed by the experiments we have extrapolations given by the initial shape model dependent not entirely reliable

32 WHERE WERE WE? in general with the data we had - High x: no constraints - Low x: extrapolations - No sensitivity to flavour separation - No sensitivity to gluon density at low nor high x

33 d a t a t y p e SET DSSZ PRD85 (2012) ncteq15 PRD93 (2016) KA15 PRD93 (2016) e-dis D-Y pions ν-dis EW jets # data points accuracy NLO NLO NNLO proton PDF MSTW2008 ~ CTEQ6.1 JR09 flavour separation? no valence only no

34 Where are we after LHC Run I?

35 WHERE ARE WE? form the ppb white paper estimations J.Phys. G39 (2012)

36 WHERE ARE WE? Before EPPS16 N. Armesto, H. Paukkunen, J.M. Penín, C. A. Salgado and P.Z., EPJ C76 (2016) no.4, 218 jets (ATLAS) charged hadrons (ALICE, CMS) and pions (ALICE) W boson (ALICE, CMS) and Z boson (ATLAS, CMS) di-jets (CMS) only the last two included in EPPS16 arxiv:

37 WHERE ARE WE? arxiv:

38 WHERE ARE WE? Z d (y Z )/d ( y Z ) No nuclear e ects ATLAS data EPPS16 Zproduction,pPb, p s =5.02 TeV 66 GeV <M`+` < 116 GeV d (y Z 0.4)/d ( y Z 0.4) CMS data No nuclear e ects EPPS16 Zproduction,pPb, p s =5.02 TeV p T (`±) > 20 GeV `± lab < GeV <M`+` < 120 GeV y Z y Z 0.4 x M Z,W p s e y arxiv:

39 WHERE ARE WE? W +/- Phys.Lett. B750 (2015) good candidate for flavour decomposition

40 WHERE ARE WE? W +/- d (y`+)/d ( y`+) CMS data No nuclear e ects EPPS16 W + production, ppb p s =5.02 TeV p T (`+) > 25 GeV d (y` )/d ( y` ) W CMS data No nuclear e ects EPPS16 production, ppb, p s =5.02 TeV p T (` ) > 25 GeV lepton rapidity (lab frame) lepton rapidity (lab frame) arxiv:

41 WHERE ARE WE? W +/- Phys.Lett. B750 (2015) good candidate for flavour decomposition arxiv:

42 WHERE ARE WE? di-jets Eur.Phys.J. C74 (2014) no.7, 2951

43 WHERE ARE WE? di-jets arxiv:

44 WHERE ARE WE? R valence arxiv:

45 WHERE ARE WE? R sea arxiv:

46 WHERE ARE WE? R gluon arxiv:

47 d a t a t y p e SET DSSZ PRD85 (2012) ncteq15 PRD93 (2016) KA15 PRD93 (2016) EPPS16 arxiv: e-dis D-Y pions ν-dis EW jets # data points accuracy NLO NLO NNLO NLO proton PDF MSTW2008 ~ CTEQ6.1 JR09 CT14NLO flavour separation? no valence only no yes!

48 WHERE ARE WE? the new set is great, but what have we learned so far?

49 WHERE ARE WE? the new set is great, but what have we learned so far? - call for flavour separation in the npdfs can be answered by data - di-jets strongly depend on proton PDFs - accurate FFs needed

50 WHERE ARE WE GOING? The future: LHC Run II RHIC EIC LHeC??

51 WHERE ARE WE GOING? TO CERN LHC: - Run I: measured pp ratios to be re-analysed, observables not considered before could be included - Run II: already a pp 8TeV, LHCb involved, new FFs to come

52 WHERE ARE WE GOING? TO BNL Aschenauer et al., arxiv: [nucl-ex] direct photon g + q! q +

53 WHERE ARE WE GOING? TO BNL Aschenauer et al., arxiv: [nucl-ex] direct photon g + q! q + R g (Pb)(x,Q 2 =1.0 GeV 2 ) 1.5 DSSZ before rew. DSSZ after rew R g (Pb)(x,Q 2 =1.69 GeV 2 ) 1.5 EPS09 before rew. EPS09 after rew x x

54 WHERE ARE WE GOING? TO BNL Aschenauer et al., arxiv: [nucl-ex] Drell-Yan

55 WHERE ARE WE GOING? TO BNL Aschenauer et al., arxiv: [nucl-ex] Drell-Yan R sea (Pb)(x,Q 2 =1.0 GeV 2 ) DSSZ before rew. DSSZ after rew x R sea (Pb)(x,Q 2 =1.69 GeV 2 ) EPS09 before rew. EPS09 after rew x

56 WHERE ARE WE GOING? TO BNL? Accardi et al., Eur.Phys.J. A52 (2016) no.9, 268 Great possibilities!

57 WHERE ARE WE GOING? TO BNL? F 2 (x,q 2 ) - log 10 (x) F 2 in e+au x = on 50 GeV 5 on 100 GeV 20 on 100 GeV F 2 World Data (A Fe) CTEQ10+EPS Ldt = 10 fb -1 /A Errors enlarged by factor F L (x,q 2 ) - log 10 (x) F L in e+au x = x = x = x = x = x = x = x = x = Ldt = 10 fb -1 /A 20 on 50,75,100 GeV 5 on 50,75,100 GeV Q 2 (GeV 2 ) Q 2 (GeV 2 ) Accardi et al., Eur.Phys.J. A52 (2016) no.9, 268

58 WHERE ARE WE GOING? TO BNL? F 2 c c (x,q 2 ) - log10 (x)/ x = F 2 c c in e+au 5 on 50 GeV 5 on 100 GeV 20 on 100 GeV CTEQ10+ EPS Never measured for ea! Ldt = 10 fb -1 /A Q 2 (GeV 2 ) Accardi et al., Eur.Phys.J. A52 (2016) no.9, 268

59 WHERE ARE WE GOING? TO BNL? J.H. Lee, IS2016, Lisbon

60 WHERE ARE WE GOING? TO BNL? R A = N (x,q 2,z) N e (x,q 2 ) N (x,q 2,z) N e (x,q 2 ) A d Sassot, Stratmann and P.Z., Phys.Rev. D81 (2010)

61 WHERE ARE WE GOING? TO CERN? Aballeira et al., J. Phys. G 39 (2012)

62 WHERE ARE WE GOING? TO CERN? Armesto, Helenius and Paukkunen, PoS DIS2016 (2016) 276

63 WHERE ARE WE GOING? TO CERN? Armesto, Helenius and Paukkunen, PoS DIS2016 (2016) 276

64 Summary several sets of npdfs available

65 Summary several sets of npdfs available strange and gluon distributions not yet well constrained by data

66 Summary several sets of npdfs available strange and gluon distributions not yet well constrained by data the LHC and RHIC crucial to study the low x region

67 Summary several sets of npdfs available strange and gluon distributions not yet well constrained by data the LHC and RHIC crucial to study the low x region EIC (LHeC?) to go further

68 ongoing and to do nuclear effects truly universal? correlated errors? more data in DY? high pt particle production? cross-sections instead of structure functions? nuclear effects for deuteron? more flexible parameterizations? higher fixed-order analyses? A-A collisions? centrality dependence? final state nuclear effects?...???

69 That s all folks!

70 That s all folks! for now