Status of high-x section

Transcription

1 Status of high-x section A. Kusina, I. Schienbein Université Grenoble Alpes/LPSC Grenoble Laboratoire de Physique Subatomique et de Cosmologie Workshop Orsay, June 9-3, 7

2 Outline Drell Yan lepton pair production in pp W production in pp Drell Yan lepton pair production in pa The large-x gluon at AFTER in pa The large-x gluon at AFTER in pp

3 Drell Yan lepton pair production in pp

4 Kinematical plan of DY at AFTER M (GeV) Drell-Yan, pp@ 6 AFTER@LHC sim 4 s lab = 5 GeV, < Y µµ < 5, p µ T - >. GeV/c, L = fb FNAL-E65 FNAL-E866 FNAL-E866 D/p x (per.) AFTER: Extend kinematic plane to very large x (and smaller x, M > GeV) Much higher statistics in the region covered by NuSea (E866) p

5 Hadron structure at large x Large-x behaviour: x f i(x,q) ~ (-x)^bi Counting rule expectations: b_u v = b_dv = 3 Currently only b_u v relatively well constrained.6 < b_uv < 3.4 Ball, Nocera, Rojo, arxiv:64.4 Down valence quark less well known.4 < b_dv < 4.6 Exponents for the sea quarks and the gluon very poorly known

6 Hadron structure at at large x " d/u! / SU(6) Spin-flavor symmetry " d/u! Scalar diquark dominance " " d/u! /5 d/u! 4µ n/µ p 4 µ n/µ p.4 pqcd power counting Local quark-hadron duality J. Qiu, NNPSS lecture 6

7 A simple ratio in the limit xf - For example: xf = -.8, M = GeV gives x =.8, x =. xf = -.8, M = 5 GeV gives x =.8, x =. In this limit with r v = d(x)/u(x) R = DY (pn) DY (pp) ' 4ū(x )d(x ) + d(x )u(x ) 4ū(x )u(x ) + d(x )d(x ) ' 4d(x ) + u(x ) 4u(x ) + d(x ) = + 4r v 4 + r v Amusing to note: /4 < R < 4 similar to the famous Nachtmann ratio for DIS structure functions /4 < F n / F p < 4

8 A simple ratio in the limit xf - For example: xf = -.8, M = GeV gives x =.8, x =. xf = -.8, M = 5 GeV gives x =.8, x =. In this limit with r v = d(x)/u(x) R d/p (x ) = DY (pd) DY (pp) = + DY (pn) DY (pp) ' 5 + r v(x ) 4 + r v (x ).! R d/p! 8 ; r v = ><.5 ; r v = >: 5 ; r v!

9 DY pseudo data compared to NLO theory Pseudo-data for the rapidity distributions using MCFM and projected experimental uncertainties (provided by Barbara) Need more information how experimental uncertainties have been obtained (stat? sys? bgd?) Add description in EoI In the figure, the experimental errors are barely visible Performed reweighting analysis using the XFitter package

10 Impact of DY pp data on proton PDFs FOM

11 Impact of DY on proton PDFs FOM p

12 Questions/Outlook/ToDo Results of the reweighting analysis in pp look very promising Potential to reduce PDF uncertainty of light quarks at small/medium x and high x ToDo: Refining discussion of large-x hadron structure models; add references Discussion of projected experimental uncertainties Include nuclear corrections for deuteron?

13 W production

14 Motivation W production close to threshold never been measured Proxy for heavy resonance searches at the LHC Potential to provides constraints on light quark sea and the valence quarks (flavor separation)

15 Predictions for W-boson production at AFTER pp W NLO NNLO Counts/year NLO NNLO Counts/year W + p l T p l T p l T > GeV ± ± 3 > GeV ± ±.5 > 3 GeV ± ±.7 ± ± ss section at NLO and NNLO integrated over the rapidity range TABLE I Cross section at NLO and NNLO integrated over the rapidity range < µ < 5 and imposing a cut p µ T > GeV in [fb]. The results have been obtained for pp collisions at p s = 5 GeV with FEWZ [98] using the CT4 PDFs [99]. The asymmetric uncertainties have been calculated using the error PDFs. The expected number of events has been obtained with a yearly luminosity of fb. 5 and

16 R W = A simple ratio in the limit of large x, x X h i W-production at AFTER is close to the threshold (In fact, it s dominated by off-shell W bosons) Both, x and x are large. In this limit: d dy (pn! W+ + W ) d dy (pp! W+ + W ) d dy (pn! W+ + W ) + d dy (pp! W+ + W ) = = [u(x ) d(x )][ū(x ) d(x )] + [ū(x ) d(x )][u(x ) d(x )] [u(x ) + d(x )][ū(x ) + d(x )] + [ū(x ) + d(x )][u(x ) + d(x )]. At y*=, x =x on has access to rs= dbar(x)/ubar(x) R W (y = ) = ( r v)( r s ) ( + r v )( + r s ) d dy (pp! W+ + W ) d dy (pd! W+ + W )

17 Questions/Outlook/ToDo Would be good to add up the event numbers for the electron and the muon channel weighted by the detection efficiencies! Do estimate the uncertainty on Rw (a quick estimate gave a 3% relative uncertainty for R which would constrain the large-x sea) A reweighting analysis would be interesting Consider the effect of Fermi motion?

18 Drell Yan lepton pair production in pa

19 Kinematical plan of DY in p-xe Drell-Yan, s lab = 5 GeV, < Y µµ < 5, p µ T - >. GeV/c, L = pb M (GeV) (per.5) 4 AFTER@LHC sim FNAL-E866 FNAL-E x (per.) AFTER: Spectacular potential to improve the current state-of-the-art Different targets can be used (here Xe)

20 Impact of DY pa data on ncteq5 NPDFs (b) d PDF FOM: Figures to be polished

21 Questions/Outlook/ToDo FOM to be polished Repeat reweighting analysis with EPPS 6 would be interesting

22 The large-x gluon at AFTER in pa

23 RpA for non-prompt J/Psi and Y R ppb.4.3. L pp = /fb, L ppb = /pb p+pb s NN = 5 GeV B J/ψ R ppb.4.3. Lpp = /fb, L ppb = /pb ϒ...9 the lumi?).... EPS9 central.8 EPS9 min./max. shadowing EPS9 min./max. EMC effect (a) y J/ψ CMS.9 EPS9 central.8 EPS9 min./max. shadowing EPS9 min./max. EMC effect Projection of the statistical uncertainties for (a) non-prompt J/ and (b) compared to typical nucl et uncertainties TODO Projected (by JPL): Same statistical plot with ncteq; uncertainties maybe do something toafter see somesubtracting uncertainties on the non-prompt J/ the bgd compared to typical npdf uncertainties (b) y CMS Massacrier,Trecziak et al Next step: reweighting analysis on pseudo data

24 Reweighting analysis using LHC5 data Prompt D production at s NN =5. TeV LHC R ppb R ppb <y cms <4. ncteq5 ncteq5 MC -4.<y cms <-.5 P T (D ) [GeV] ncteq5 rwgt LHCb data HELAC-Onia. R ppb Prompt D production at s NN =5. TeV LHC LHCb data y cms (D ) ncteq5 ncteq5 MC ncteq5 rwgt P T < HELAC-Onia.

25 Reweighting analysis using LHC5 data.6.4 pdf replica rwgt. g Pb (x)/g p (x).8.6 HELAC-ONIA.4. Q=.3E+ GeV x

26 Questions/Outlook/ToDo This is work in progress but looks promising Currently doing a reweighting analysis with D-meson and J/Psi data in ppb collisions at LHC5 (LHCb, ALICE,...) This constrains the gluon at small-x! Will use the same procedure with AFTER pseudo data for pa. Need to validate this method for the AFTER kinematics (large-x! how important is the gg-channel?)

27 The large-x gluon at AFTER in pp

28 PROSA study O. Zenaiev et al, EPJC75(5)396 NLO QCD analysis of impact of data for heavy quark production in ep and pp collisions on PDFs Theory for heavy quark production in ep, pp: FFNS at NLO Data: HERA: Inclusive DIS cross sections in ep HERA: Heavy flavour production cross sections in ep LHCb: Differential cross sections for c (D, D +, D *+, Ds +, Λc) and b (B +, B, Bs ) production in pp at LHC7 Result: LHCb data impose constraints on low-x gluon and quark sea

29 NLO QCD predictions for charm LHCb data [µb/gev] dσ/dp pp T D < p T < 3. GeV [µb/gev] dσ/dp T 5 5 PROSA central ( µ =µ =µ ) µ. µ.5 µ. µ.5 r f f 4. < p T < 5. GeV f [µb/gev] dσ/dp T r 7. < p T r < 8. GeV Ratio Ratio Ratio y y y Central scale μ = mt (dσ/dy) (dσ/dy.5 Large scale uncertainties!.5 4. < p T < 5. GeV (dσ/dy) (dσ/dy < p T Mostly change the normalization, shape less affected < 8. GeV

30 NLO QCD predictions for charm LHCb data (dσ/dy) (dσ/dy.5. < p T < 3. GeV (dσ/dy) (dσ/dy.5 4. < p T < 5. GeV (dσ/dy) (dσ/dy.5 7. < p T < 8. GeV Ratio y Ratio y Ratio y Normalized cross sections w.r.t. dσ/dy in the bin 3<y<3.5 Shape remains sensitive to gluon Figure 6: NLO QCD predictions for charm LHCb data with different scale choices for absolute (top) and normalised (bottom) cross sections. Lower inlets indicate the ratio of predictions to the centralvery scale choice. small scale The predictions uncertainties are obtained now! by using the FFNS variant of MSTW 8 PDFs [44] with N f = 3; the charm mass is set to m c =.5GeV.

31 Results for the gluon and the sea x g x g PROSA PROSA NLO NLO FFNS FFNS fit fit µ f = µ GeV f = GeV HERA HERA DIS DIS HERA HERA DIS + DIS LHCb + LHCb abs abs HERA HERA DIS + DIS LHCb + LHCb norm norm x Σ 5 PROSA NLO FFNS fit µ f = GeV HERA DIS HERA DIS + LHCb abs HERA DIS + LHCb norm 5 δg/g δg/g δσ/σ x x x The uncertainties on the gluon and the sea are significantly x u v x u v reduced.6 HERA using DIS data HERA DIS + LHCb abs.4 In the normalised case by a factor 3 at x~5x PROSA PROSA NLO NLO FFNS FFNS fit fit HERA DIS µ f = µ GeV f = GeV HERA DIS + LHCb abs HERA DIS + LHCb norm HERA DIS + LHCb norm x d v x d v PROSA PROSA NLO NLO FFNS FFNS fit fit µ f = µ GeV f = GeV HERA DIS HERA DIS HERA DIS + LHCb abs HERA DIS + LHCb abs HERA DIS + LHCb norm HERA DIS + LHCb norm v v

32 Questions/Outlook/ToDo Work to be done! The differential cross sections have very large scale uncertainties Use normalized cross sections (as in PROSA) Ry = (dσ ppb /dy)/(dσ ppb /dy(y)) Directly sensitive to nuclear gluon and sea PDF Advantage: a lot of experimental systematics cancel

33 Questions/Outlook/ToDo Need careful comparison with state-of-theart extractions of the large-x gluon using t-tbar data to see whether AFTER can have an impact!

34 Thank you

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