Topics on QCD and Spin Physics (fourth lecture) Rodolfo Sassot Universidad de Buenos Aires HUGS, JLAB June
QCD in a nuclear medium no much interest before 98: low energy scales freeze QCD dof European Muon Collaboration (EMC) incoherence hypothesis F A ZF p +(A Z)F n A F A F D incoherence? only nucleons? free nucleons?
why npdfs? precise knowledge required for PDFs: F n (x, Q ) F νfe (x, Q ) baseline for RHIC and LHC nuclear collisions what about FFs? hadronization in a different environment hadrons and jets as nuclear matter probes
ndis phenomenology Q q x A Q p A q <x A < x N Ax A x N = Q p N q <x N <A p N = p A /A JLAB E3-3 94.4448 A F A (x N,Q ) F D(x N,Q ) =? C / D.. Q =4.6 Q =4.5 Q =4.83 Q =5.33 Q =6.5 Fermi motion.9 EMC effect..3.7.9
anti- He/D Be/D EMC effect shadowing NMC E-39 C/D Al/D F A / F D Ca/D Fe/D Ag/D Au/D shadowing - - - - x N
.75 x=.5 x=.75 x=.5.75 x=.35 x=.45 x=.55 F Sn /F C.75 x=.7 x=.9 x=.5.75 x=.75 x=.5 x=.35.75 x=5 x=5 x=.7 Q
Explaining nuclear effects convolution models: rescaling models: recombination models: photon fluctuations: smeared nucleons, pions, etc. x-effective mass Q -effective scale partonic-like interactions vector mesons, q-qbar,... a non trivial superposition?
A factorized pqcd approach: dσ A = ˆσ i f A i df A i (x N,Q ) dlogq = α s π x N dy y f A j (y, Q )P ij ( xn y ) partonic standard nonperturbative universal dσ N = ˆσ i f N i can we split fi A? not probability densities can we fit fi A?
Global QCD fits for npdfs: fixed-q, models EKS98 LO HKN LO nds NLO convolutions f A i (x N,Q )=R i (x N,Q, A, Z) f i (x N,Q ) f A i (x, Q )= A x dy W A i (y, Q ) f i ( x y,q ) W A i (y, Q )=δ( y) W A i (y, Q )=δ( ɛ y) W A i (y, Q )=n i y α i ( y) β i no effects shift/rescaling enhancement/supression n i = λ n i + γ n i A δn i λ n i, γ n i, δ n i
Global QCD fits for npdfs: He/D Be/D NMC E-39. C/D Ca/D C/D Al/D F A / F D Ca/D Fe/D DY DY A / D.9. Fe/D W/D Ag/D Au/D.9 - - - - - x T - x N DIS rates to D Drell Yan rates to D
Global QCD fits for npdfs: Be/C Al/C.75 x=.5 x=.75 x=.5 NMC Ca/C Fe/C.75 x=.35 x=.45 x=.55 F A / F C F Sn /F C.75 x=.7 x=.9 x=.5 Pb/C Sn/C.75 x=.75 x=.5 x=.35 - - x N - -.75 x=5 x=5 x=.7 Q DIS rates to C scale dependence
Global QCD fits for npdfs:...5 3, 4.5 " v " s a v a g F Sn /F C.75.75.75 x=.5 x=.75 x=.5 x=.35 x=.45 x=.55 x=.7 x=.9 x=.5 # s -.5 a s.75 x=.75 x=.5 x=.35 # v A -. A.75 x=5 x=5 x=.7 Q scale dependence W v (y, A, Z) =A [ a v δ( ɛ v y)] + n v (ya) α v ( ya) β v
R A i (x, Q ) f A i (x, Q ) f i (x, Q ) Pb Pb Pb =.69 GeV ) (, Pb.4... Q =.69 GeV.4... = GeV ) (, Pb.4.... This work, EPS9NLO HKN7 (NLO) nds (NLO) -4-3 - - Q = GeV -4-3 - -.4... -4-3 - -.
nff Phenomenology: Early evidence: SLAC Phys.Rev.Lett. 4, 64 (978) EMC Z.Phys. C5, (99) E665 Phys.Rev. D5, 836 (994) Precise SIDIS: HERMES Nucl. Phys.B 78 (7); Precise : PHENIX Phys.Rev.Lett.98 73 (7). STAR Phys.Lett.B66, 8 (5) B637, 6 (6)
.4..4..4..9 3 4 5 6 7 8 9.9 3 4 5 6 7 8 9.9 3 4 5 6 7 8 9 nff Phenomenology: h R A. He Ne Kr Xe + Precise SIDIS: HERMES Nucl. Phys.B 78 (7); R(z, Q, ν) = ( ( N sidis N inc )A N sidis N inc )D... " (GeV) z K + p Q (GeV )
nff Phenomenology: PHENIX Phys.Rev.Lett.98 73 (7). 3 d 3 " E dp 3 [mb / GeV ] - - -3-4 -5-6.4. R " FF (nds) FF (EPS) PHENIX R " FF (nds) FF (EPS) E d 3 " dp 3 [mb / GeV ] STAR prel. (thesis) STAR Phys.Lett.B66, 8 (5) B637, 6 (6) O.Grebenyuk, Ph.D.Thesis, arxiv:99.36. 3 - - -3-4 5 5 d 3 " dp 3 + E [mb / GeV ] STAR 5 5 FF (nds) FF (EPS) d 3 " dp 3 - E [mb / GeV ] STAR.6.4 R " + R " - R H σ (A, ) A Ed 3 σ H /dp 3 da Ed 3 σ h /dp 3 pp. 4 6 8 4 6 8
.4..4..4..9 3 4 5 6 7 8 9.9 3 4 5 6 7 8 9.9 3 4 5 6 7 8 9 R A h. nff Phenomenology: PHENIX Phys.Rev.Lett.98 73 He (7). Kr. STAR Phys.Lett.B66, 8 (5) B637, 6 (6) O.Grebenyuk, Ph.D.Thesis, arxiv:99.36... Hermes Ne " (GeV) Xe + z K + p Q (GeV ) 3 d 3 " E dp 3 [mb / GeV ] - - -3-4 -5-6.4. 3 - - -3-4.6.4 R " FF (nds) FF (EPS) PHENIX 5 5 d 3 " dp 3 + E [mb / GeV ] STAR R " + R " FF (nds) FF (EPS) E d 3 " dp 3 [mb / GeV ] STAR prel. (thesis) 5 5 FF (nds) FF (EPS) d 3 " dp 3 - E [mb / GeV ] STAR R " - R H σ (A, ) A Ed 3 σ H /dp 3 da Ed 3 σ h /dp 3 pp. 4 6 8 4 6 8
Do nuclear effects factorize into FFs? nffs factorize all non-perturbative details? universal (interchangeable)? well defined framework beyond LO? constrained by data through global NLO fit? Why it could not work: factorization breaking non universality of hadronization modified energy scale dependence nuclear/high density higher twists
npdfs digression: EPS npdfs K.Eskola, H.Paukkunen, C.A.Salgado, JHEP94, 65 (9) designed to reproduce data 3 d 3 " E dp 3 [mb / GeV ] - - -3-4 -5-6.4. R " FF (nds) FF (EPS) PHENIX nds npdfs 5 5 D.de Florian R.S. Phys.Rev.D69 748 (4)
npdfs digression: EPS npdfs K.Eskola, H.Paukkunen, C.A.Salgado, JHEP94, 65 (9) designed to reproduce data (assuming no FF effects) unusual gluons extra normalizations: (?) STAR.9 PHENIX.3 R =.69 GeV ) (, Pb = GeV ) (, Pb.4.3....9.7.4....4.... y= PHENIX 7 STAR 6 + + - EPS9NLO 4 6 8 4 6 This work, EPS9NLO HKN7 (NLO) nds (NLO) -4-3 - - Q =.69 GeV Q = GeV -4-3 - - Pb Pb Pb.4....4... -4-3 - -.
Baseline: consistency nds npdfs D.de Florian, R.S. Phys.Rev.D69 748 (4) reference DSS FFs D.de Florian, R.S., M.Stratmann Phys.Rev.D75 4 (7) Phys.Rev.D76 7433 (7) - - -3 d 3 " E dp 3 [mb / GeV ] Hermes /N DIS dn " + /dzdq z - bin.5 -.35.35-5.5 z.35 " + " -.. -. -. pp reference -4-5 -6-7 -8-9 - THIS FIT KRE AKK scale uncertainty PHENIX data (preliminary) (data - theory)/theory - - THIS FIT KRE /N DIS dn " - /dzdq not fitted 5 - -.75 z - bin.5 -.35.35-5 5 - -.75.35 z 5 5 z z.75.. -. -... -. -... -. -. (data - theory)/theory sidis reference 5 5 Q Q
Baseline: consistency nds npdfs D.de Florian, R.S. Phys.Rev.D69 748 (4) reference DSS FFs D.de Florian, R.S., M.Stratmann Phys.Rev.D75 4 (7) Phys.Rev.D76 7433 (7) LHC-CMS - s=9 GeV s=.36 TeV CMS s=9 GeV CMS s=.36 TeV DSS NLO - 4 " =.3 " =. " =.9 " =.7 4 " =.3 " =. " =.9 " =.7 low pt CMS data " =.5 " =.5 " =.3 " =.3-3 " =. " =.9 " =. " =.9 " =.7 " =.7-4 scale uncertainties s=.36 TeV s=9 GeV " = " =.3 " =. " = " =.3 " =. CMS arxiv:.6.5.5 3 3.5 4 (GeV).5.5
Baseline: consistency nds npdfs D.de Florian, R.S. Phys.Rev.D69 748 (4) reference DSS FFs D.de Florian, R.S., M.Stratmann Phys.Rev.D75 4 (7) Phys.Rev.D76 7433 (7) LHC - ATLAS CMS s=9 GeV CMS s=.36 TeV - s=9 GeV DSS NLO - -3 4 " =.3 " =. " =.9 " =.7 4 " =.3 " =. " =.9 " =.7 low pt CMS data -4 " =.5 " =.5 " =.3 " =.3-5 " =. " =. -6 " =.9 " =.7 " =.9 " =.7 ATLAS arxiv:3.34-7 -8 " = " =.3 " =. " = " =.3 " =. CMS arxiv:.6.7.9 3 4 5 6 7 8 9 (GeV.5.5
Fitting nffs: convolution approach revisited D h i/a (z, Q )= z dy W i (y, A, Q ) D h i ( z y,q ) works for npdfs re-scalings/shifts modifies FFs natural language NLO W i (y, A, Q )=δ( y) W i (y, A, Q )=δ( ɛ y) W i (y, A, Q )=n i y α i ( y) β i no effects z-shift (energy loss) enhancement/suppression, re-shape weighting coefficients ɛ i,n i, α i, β i with a smooth A dependence n i = λ n i + γ n i A δn i with λ n i, γ n i, δ n i parameters to be fitted A very simple example for pion production:
Toy parameterization normalization & trend HERMES Nucl. Phys.B 78 (7); R A R He Ne Kr Xe.5.75.5.75.5.75.5.75 z z z z + - not flexible enough for x-dependence: gluons? R A R +.5...5...5...5.. x x x x - no conflict with standard evolution R A R +.5 5 7.5.5 5 7.5.5 5 7.5.5 5 7.5 Q [GeV ] Q [GeV ] Q [GeV ] Q [GeV ] - NLO with DS npdfs idem + toy nffs
Toy parameterization 3 d 3 " E dp 3 [mb / GeV ] - - -3-4 -5-6 nff * (nds) FF (nds) FF (EPS) PHENIX nff * (nds) FF (nds) FF (EPS) E d 3 " dp 3 [mb / GeV ] STAR prel. (thesis).4 R " R " pt dependence. quark/gluon interplay χ /d.o.f. - - -3-4 5 5 3 + d 3 " E dp 3 [mb / GeV ] nff * (nds) STAR 5 5 FF (nds) FF (EPS) - d 3 " E dp 3 [mb / GeV ] STAR.6.4 R " + R " -. 4 6 8 4 6 8
Refined parameterization quark fragmentation Wq H (y, A, Q ) = n q y α q ( y) β q + n qδ( ɛ q y) Wg H (y, A, Q ) = n g y α g ( y) β g + n gδ( ɛ g y) gluon fragmentation n i = λ n i + γ n i A δn i smooth A-dependence λ n λ n vanishing effects as A 4 parameters
χ = 396. 38 data points 4 parameters χ /d.o.f =.8 R A.5.75.5.75.5.75.5.75 z z z z R He Ne Kr Xe + - z and x dependence R A R + -.5...5...5...5.. x x x x no conflict with standard evolution R A R + -.5 5 7.5.5 5 7.5.5 5 7.5.5 5 7.5 Q [GeV ] Q [GeV ] Q [GeV ] Q [GeV ]
χ = 396. 38 data points 4 parameters χ /d.o.f =.8 3 d 3 " E dp 3 [mb / GeV ] - - -3-4 -5-6.4. R " nff (nds) nff * (nds) FF (nds) FF (EPS) PHENIX R " nff (nds) nff * (nds) FF (nds) FF (EPS) E d 3 " dp 3 [mb / GeV ] STAR prel. (thesis) good description: normalization pt dependence 3 - - -3-4 5 5 d 3 " dp 3 E [mb / GeV ] nff (nds) nff * (nds) + STAR 5 5 FF (nds) FF (EPS) d 3 " dp 3 - E [mb / GeV ] STAR.6.4 R " + R " -. 4 6 8 4 6 8
z-dependence R q = D q/a(z, Q ) D q/p (z, Q ) quarks mimic SIDIS.5 R q hic sunt dracones hic sunt dracones z D q/a He Ne Kr Xe Au. gluons do the opposite R g hic sunt dracones Q = GeV hic sunt dracones z D g/a.. z. z low z behavior not supported by data: artifact?
Next steps: pqcd factorizable scheme with effective npdf & nff (NLO) A, x, z, Q, ν and pt-dependence of DIS, SIDIS and dau data effective npdf & nff as tools for distilling data predictions based on npdf and nff can be tested/refined JLAB, RHIC, LHC and in the future at EIC constraints gluon and sea npdf nff final state hadrons jet physics in a nuclear environment factorization breaking in hot/dense nuclear medium