nCTEQ15 nuclear parton distributions with uncertainties [DOI: - PowerPoint PPT Presentation

nCTEQ15 nuclear parton distributions with uncertainties [DOI: 10.1103/PhysRevD.93.085037] Tomáš Ježo Università di Milano-Bicocca INFN, Sezione di Milano-Bicocca In collaboration with: A. Kusina, K. Kova ř ík, D. B. Clark, C. Keppel, F. Lyonnet, J. Morfín, F. I. Olness, J. Owens, I. Schienbein, J. Y. Yu 14 June 2016

[DOI: 10.1103/PhysRevD.93.085037] Introduction structure of nuclei ▸ Parton Density Functions (PDFs) = ▹ Describe the structure of nucleons ▹ f(x,Q) ; x momentum fraction, Q scale ▹ Q dependence calculable ▹ x dependence obtained from a fi t to data ▸ Nuclear Parton Density Functions (nPDFs) ▹ Describe the structure of nuclei BCDMS(85) ▹ Nucleus not just and ensamble BCDMS(87) SLAC/NMC param. SLAC-E049(83) SLAC-E139(94) SLAC-E140(94) of free nucleons EMC dip D ⬥ weighted average over 2 Fe protons and neutrons 2 ⬥ nuclear correction

[DOI: 10.1103/PhysRevD.93.085037] Introduction structure of nuclei ▸ Nuclear Parton Density Functions (nPDFs) ▹ Describe the structure of nuclei ▹ Nucleus not just and ensamble of free nucleons ⬥ weighted average over protons and neutrons ⬥ nuclear correction ▸ We fi t data from collisions of nuclei to obtain nPDFs ▹ Factorization & DGLAP evolution ⬥ Allows for a de fi nition of universal (n)PDF ▹ Isospin symmetry ▹ Bound proton PDFs: same evolution and sum rules as free proton PDFs (neglecting contributions from x > 1 region) ▹ Observables calculated as

[DOI: 10.1103/PhysRevD.93.085037] Introduction available nPDFs ▸ Multiplicative nuclear correction factors ▹ HKN : Hirai, Kumano, Nagai [PRC 76, 065207 (2007), arXiv:0709.3038] ▹ EPS : Eskola, Paukkunen, Salgado [JHEP 04 (2009) 065, arXiv:0902.4154] ▹ DSSZ : de Florian, Sassot, Stratmann, Zurita [PRD 85, 074028 (2012), arXiv:1112.6324] ▸ Native nuclear PDFs ▹ nCTEQ [PRD 80, 094004 (2009), arXiv:0907.2357, arXiv:1509.00792]

[DOI: 10.1103/PhysRevD.93.085037] Introduction nCTEQ framework ▸ Functional form of the bound proton PDF same as for the free proton (CTEQ6M, x restricted to 0 < x < 1 ) ▸ A -dependent fi t parameters (reduces to free proton for A = 1 ) ▸ PDFs for nucleus (A, Z) (bound neutron PDF by isospin symmetry)

[DOI: 10.1103/PhysRevD.93.085037] Fit data sets ▸ NC DIS & DY ▸ Single pion production (new) ▸ Neutrino (to be included later)

[DOI: 10.1103/PhysRevD.93.085037] Fit methods and parameters ▸ Fit properties: ▸ Kinematic cuts: ▹ fi t @NLO ▹ ▹ ▹ ACOT heavy quark ▹ 708 (DIS & DY) + 32 ( ) scheme = 740 data points after cuts ▸ Error analysis: ▸ 16+2 free parameters ▹ use Hessian method ▹ 7 gluon ▹ tolerance (every ▹ 7 valence nuclear target within 90% ▹ 2 sea C.L.) ▹ 2 pion data normalizations

[DOI: 10.1103/PhysRevD.93.085037] Fit quality of the fi t

[DOI: 10.1103/PhysRevD.93.085037] Results impact of data ▸ Compare nCTEQ fi ts: ▸ Bound proton PDFs ▹ nCTEQ with data ▹ nCTEQnp without data

[DOI: 10.1103/PhysRevD.93.085037] Results impact of data ▸ Compare nCTEQ fi ts: ▸ Bound proton PDFs ▹ nCTEQ with data ▹ nCTEQnp without data

[DOI: 10.1103/PhysRevD.93.085037] Results impact of data ▸ Compare nCTEQ fi ts: ▸ Nuclear correction factor ▹ nCTEQ with data ▹ nCTEQnp without data

[DOI: 10.1103/PhysRevD.93.085037] Results comparison with other fi ts ▸ Compare with other fi ts: ▸ Nuclear correction factor ▹ nCTEQ15 ▹ EPS09 ▹ DSSZ ▹ HKN07

[DOI: 10.1103/PhysRevD.93.085037] Results comparison with other fi ts ▸ Compare with other fi ts: ▸ Bound proton PDFs ▹ nCTEQ15 ▹ EPS09 ▹ DSSZ ▹ HKN07

[DOI: 10.1103/PhysRevD.93.085037] Results valence distributions

[DOI: 10.1103/PhysRevD.93.085037] Results valence distributions ▸ for and fi ts is very similar (~590) ⇒ no preference for either of the solutons in the data ▸ Di ff erences between u and d valence distributions washed out in the nuclei ▸ Hessian error analysis does not account for this ⇒ one solution not in the error band of the other solution

[DOI: 10.1103/PhysRevD.93.085037] Results valence distributions ▸ Full lead nucleus distribution

[DOI: 10.1103/PhysRevD.93.085037] Results description of fi tted data

[DOI: 10.1103/PhysRevD.93.085037] Results description of fi tted data

[DOI: 10.1103/PhysRevD.93.085037] Results description of fi tted data

[DOI: 10.1103/PhysRevD.93.085037] Results description of fi tted data

[DOI: 10.1103/PhysRevD.93.085037] Results description of fi tted data

[DOI: 10.1103/PhysRevD.93.085037] Summary ▸ error PDFs released: ▹ Available on the nCTEQ website: http://ncteq.hepforge.org (and LHAPDF) ▹ T wo fi ts provided: with and without pion production data ▸ Di ff erences in valence distributions observed ▹ Impact of di ff erent assumptions entering nPDF analyses ▹ Uncertainties are strongly underestimated (assumptions replace uncertainties) ▸ Regardless of big di ff erences in valence distributions the fi tted data described very well

[DOI: 10.1103/PhysRevD.93.085037] Summary ▸ error PDFs released: ▹ Available on the nCTEQ website: http://ncteq.hepforge.org (and LHAPDF) ▹ T wo fi ts provided: with and without pion production data ▸ Di ff erences in valence distributions observed ▹ Impact of di ff erent assumptions entering nPDF analyses ▹ Uncertainties are strongly underestimated (assumptions replace uncertainties) ▸ Regardless of big di ff erences in valence distributions the fi tted data described very well

[DOI: 10.1103/PhysRevD.93.085037] Outlook recent developments ▸ Study the impact of LHC data employing reweighting +/- ▹ rapidity distribution of charged leptons in W