s , ABM PDFs, and quark masses S.Alekhin ( Univ. of Hamburg & - PowerPoint PPT Presentation

α s , ABM PDFs, and quark masses S.Alekhin ( Univ. of Hamburg & IHEP Protvino) sa, Blümlein, Moch, Plačakytė PRD 96, 014011 (2017) sa, Blümlein, Moch PLB 777, 134 (2018) sa, Blümlein, Moch EPJC 78, 477 (2018) sa, Kulagin, Blümlein, Moch, Petti hep-ph/1808.06871 sa, Blümlein, Moch hep-ph/1808.08404 alphas2019, Trento, 12 Feb 2019 1

PDF fit framework QCD evolution massless NNLO, massive NLO OMEs (OPENQCDRAD) 3-flavour PDFs 5-flavour PDFs DIS inclusive t-quark Drell-Yan (W,Z, γ ) DIS heavy quark NNLO (Hathor, fasttop) NNLO(approx.) NNLO (OPENQCDRAD) (OPENQCDRAD) (FEWZ-grids) Power corr. (TMC+high-twist) 2

Data used and fit quality 3

DY data in the ABMP16 fit Good overall agreement in NNLO with some tension between D0 and LHCb data No impact on α s 4

Deuteron effects in the PDF fits Spread between different deuteron models O(%); sizable for the precision measurements DY data help to keep accuracy of the PDF determination avoiding uncertainty due to modeling of nuclear effects 7

Recent progress in massive DIS coefficients Combination of the soft gluon resummation, large-energy asymptotic and available NNLO massive OMEs – update with the pure singlet massive OMEs improves theoretical uncertainties sa, Moch, Blümlein PRD 96, 014011 (2017) 6

HERA charm data, m c and α s H1/ZEUS ZPC 73, 2311 (2013) Χ 2 /NDP=66/52 m c (m c )=1.252±0.018(exp.)-0.01(th.) GeV ABMP16 m c (pole)~1.9 GeV (NNLO) Marquard et al. PRL 114, 142002 (2015) RT optimal Χ 2 /NDP=82/52 MMHT14 EPJC 75, 204 (2015) m c (pole)=1.25 GeV S-ACOT- χ Χ 2 /NDP=59/47 CT14 PRD 93, 033006 (2016) m c (pole)=1.3 GeV F0NLL Χ 2 /NDP=60/47 NNPDF3.0 JHEP 504, 040 (2015) m c (pole)=1.275 GeV F0NLL Χ 2 /NDP=54/37 (Q 2 >8 GeV2) NNPDF3.1 hep-ph/1706.00428 m c (pole)=1.51 GeV, intrinsic (fitted) charm FFNS works better, particularly at small Q H1, ZEUS EPJC 78, 473 (2018) m c (m c )=1.246±0.023 (h.o.) GeV NNLO α s is pulled up if the VFN scheme is used Kiyo, Mishima, Sumino PLB 752, 122 (2016) m c (m c )=1.279±0.008 GeV Thorne, NNPDF Kühn, LoopsLegs2018 7

α s from DIS combination of the DY data (disentangle PDFs) and the DIS ones (constrain α s ) Run-II HERA data pull α s up by 0.001 the value of α s is still lower than the PDG one: pulled up by the SLAC and NMC data; pulled down by the BCDMS and HERA ones only SLAC determination overlap with the PDG band provided the high-twist terms are taken into account 8

High twists in DIS 9 Virchaux, Milsztajn PLB 274, 221 (1992)

High twists at small x F 2,T =F 2,T (leading twist) + H 2,T (x)/Q 2 H(x)=x h P(x) Controlled by SLAC data sa, Blümlein, Moch PRD 86, 054009 (2012) H T (x) continues a trend observed at larger x; H 2 (x) is comparable to 0 at small x h T =0.05 ± 0.07 → slow vanishing at x → 0 No dramatic increase of F L at small x Alternative explanations are considered: resummation, saturation, etc. 10

Correlation of α S with twist-4 terms The value of α S and twist-4 terms are strongly correlated With HT=0 the errors are reduced → no uncertainty due to HTs With account of the HT terms the value of α S is stable with respect to the cuts MRST: α S (M Z )=0.1153(20) (NNLO) (W 2 >15 GeV 2 , Q 2 > 10 GeV 2 ) A stringent cut on Q is necessary for the fit with HT=0 Moch et al. hep-ph/1405.4781 11

Impact of t-quark data α s (M Z )=0.1145(9) → 0.1147(8) Running t-quark mass can be determined simultaneously** m t (m t )= 160.9 ± 1.1 GeV m t (pole)=170.4 ± 1.2 GeV m t (MC)~172.5 GeV from LHC ABMP16 updated (see Rabbertz’s talk) (Hoang et al. try to quantify the difference) ** Running-mass definition provides better perturbative stability (Extras) 12

Electroweak vacuum stability Buttazzo et al., JHEP 12, 089 (2013 ) mr: Kniehl, Pikelner, Veretin CPC 206, 84 (2016 ) Vacuum stability is quite sensitive to the t-quark mass; stability is provided up to Plank-mass scale using α s and m t in a consistent way. 13

t-quark mass from the single-top production Electroweak production → reduced impact of α s and the PDF umcertainties HATHOR framework t-channel: NNLO Brucherseifer, Caola, Melnikov PLB 736, 58 (2014) s-channel: NNLO threshold. resum. Different PDFs prefer value of m t (m t ) ~ 160 ± 3.5 GeV NNPDF goes higher by 3 GeV. The CT14 and MMHT14 go higher by 3 GeV with the ttbar channel PDFs fixed sa, Moch, Thier PLB 763, 341 (2016) 14

Data set used for the PDF shape study sa, Blümlein, Moch PLB 777, 134 (2018) sa, Blümlein, Kulagin, Moch, Petti hep-ph/1808.06871 The ABMP16 framework with: – DY data replaced by the deuteron ones ⇒ comparable quark disentangling at moderate and large x – t-quark data excluded (no relevance for the first estimates) 15

Checking styles of PDF shape ABMP16 CJ15 CT10 CT14 epWZ16 MMHT14 N PDF 28 21 26 26 14 31 2 (GeV 2 ) 9 1.69 1.69 1.69 1.9 1 μ 0 χ 2 4065 4108 4148 4153 4336 4048 PDF shape x α (1-x) β x α (1-x) β P(x,√x) x α (1-x) β x α (1-x) β x α (1-x) β P(x,√x) x α (1-x) β P(x,√x) exp[P(x,ln(x))] exp[P(x,√x)] exp[P(x,√x)] Constraints ū=đ (x→0) α uv =α dv α uv =α dv α ū =α đ =α s α ū =α đ =α s β uv =β dv ū=đ (x→0) ū=đ (x→0) α ū =α đ =α s α s (M Z ) 0.1153 0.1147 0.1150 0.1160 0.1162 0.1158 Various PDF-shape modifications provide comparable description with N PDF ~30 Some deterioration, which happens in cases is apparently due to constraints on large(small)-x exponents Conservative estimate of uncertainty in α s (M Z ): 0.0007, more optimistic: 0.0003 16

Test fit with the neural network shape Valence u-quark is modeled by x α (1-x) β NN(x), where NN is neural network with 37 parameters (NNPDF3.0 ansatz), other PDFs use MMHT14 shape Result is in quite agreement with the MMHT14 shape x α (1-x) β P(x) with 4 paramters in P(x) ⇒ no particular flexibility is provided by neural network Study of sea and gluon distribution in progress, the same behaviour expected 17

Summary α s (M Z )=0.1147(8) is obtained in the ABMP16 PDF fjt – ~1σ larger than the earlier value due to impact of the HERA I+II and ttbar data (uncertainty reduces as well) – m c (m c )=1.252 ±0.018(exp.)-0.01(th.) GeV in nice agreement with other determinations: good indication of the consistent FFN scheme description, while VFN scheme pulls α s up – the high-twist terms still play important role: larger value of α s if not taken into account – m t (m t )= 160.9 ± 1.1 GeV m t (pole)=170.4 ± 1.2 GeV : EW vacuum stability up to the Plank scale Uncertainty due to PDF shape variation can be roughly estimated as ~0.0005 Uncertainty due to nuclear corrections is negligible since no deuteron data are included and other samples (charm CC productions) are not sensitive to α s 18

EXTRAS 19

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Modeling NNLO massive coefficients small s small x s ξ =Q 2 /m 2 η=s/4m 2 -1 large Q 2 Combination of the threshold corrections (small s), high-energy limit (small x), and the NNLO massive OMEs (large Q 2 ) Kawamura, Lo Presti, Moch, Vogt NPB 864, 399 (2012) 22

Impact of high twists on SLAC data sa, Blümlein, Moch PRD 86, 054009 (2012) Power-like terms affect comparison even with a “safe” cut W 2 ≥ 12.5 GeV 2 23

Impact of the t-quark data on the ABMP16 fit Pole MSbar HATHOR (NNLO terms are checked with TOP++) Langenfeld, Moch, Uwer PRD 80, 054009 (2009) Running mass definition provides nice perturbative stability Czakon, Fiedler, Mitov PRL 110, 252004 (2013) 24

Single-top data ABMP16 updated 25

Parameter number redundancy Uncertainties explodes if extra PDF parameters are used 26