s , ABM PDFs, and quark masses S.Alekhin ( Univ. of Hamburg & - - PowerPoint PPT Presentation
s , ABM PDFs, and quark masses S.Alekhin ( Univ. of Hamburg & IHEP Protvino) sa, Blmlein, Moch, Plaakyt PRD 96, 014011 (2017) sa, Blmlein, Moch PLB 777, 134 (2018) sa, Blmlein, Moch EPJC 78, 477 (2018) sa, Kulagin, Blmlein,
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alphas2019, Trento, 12 Feb 2019 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
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QCD evolution massless NNLO, massive NLO OMEs (OPENQCDRAD) DIS inclusive NNLO (OPENQCDRAD) Power corr. (TMC+high-twist) t-quark (Hathor, fasttop) Drell-Yan (W,Z,γ) NNLO (FEWZ-grids) DIS heavy quark NNLO(approx.) (OPENQCDRAD) 5-flavour PDFs 3-flavour PDFs
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Good overall agreement in NNLO with some tension between D0 and LHCb data No impact on αs
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
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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)
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Χ2/NDP=66/52 mc(mc)=1.252±0.018(exp.)-0.01(th.) GeV ABMP16 mc(pole)~1.9 GeV (NNLO) RT optimal Χ2/NDP=82/52 mc(pole)=1.25 GeV S-ACOT-χ Χ2/NDP=59/47 mc(pole)=1.3 GeV F0NLL Χ2/NDP=60/47 mc(pole)=1.275 GeV F0NLL Χ2/NDP=54/37 (Q2>8 GeV2) mc(pole)=1.51 GeV, intrinsic (fitted) charm
H1/ZEUS ZPC 73, 2311 (2013) Kiyo, Mishima, Sumino PLB 752, 122 (2016) MMHT14 EPJC 75, 204 (2015) NNPDF3.1 hep-ph/1706.00428 CT14 PRD 93, 033006 (2016)
Marquard et al. PRL 114, 142002 (2015)
NNPDF3.0 JHEP 504, 040 (2015)
mc(mc)=1.246±0.023 (h.o.) GeV NNLO FFNS works better, particularly at small Q
Kühn, LoopsLegs2018
mc(mc)=1.279±0.008 GeV
H1, ZEUS EPJC 78, 473 (2018)
αs is pulled up if the VFN scheme is used Thorne, NNPDF
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combination of the DY data (disentangle PDFs) and the DIS ones (constrain αs ) Run-II HERA data pull αs up by 0.001 the value of αs is still lower than the PDG one: pulled up by the SLAC and NMC data; pulled down by the BCDMS and HERA ones
terms are taken into account
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Virchaux, Milsztajn PLB 274, 221 (1992)
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HT(x) continues a trend observed at larger x; H2(x) is comparable to 0 at small x hT=0.05±0.07 → slow vanishing at x → 0 F2,T=F2,T(leading twist) + H2,T(x)/Q2 H(x)=xhP(x) Controlled by SLAC data
sa, Blümlein, Moch PRD 86, 054009 (2012)
No dramatic increase of FL at small x Alternative explanations are considered: resummation, saturation, etc.
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The value of αS 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 αS is stable with respect to the cuts MRST: αS(MZ)=0.1153(20) (NNLO) (W2>15 GeV2, Q2> 10 GeV2)
A stringent cut on Q is necessary for the fit with HT=0
Moch et al. hep-ph/1405.4781
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αs(MZ)=0.1145(9) → 0.1147(8) Running t-quark mass can be determined simultaneously** mt(mt)= 160.9± 1.1 GeV mt(pole)=170.4± 1.2 GeV mt(MC)~172.5 GeV from LHC (see Rabbertz’s talk) (Hoang et al. try to quantify the difference) ** Running-mass definition provides better perturbative stability (Extras) ABMP16 updated
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Vacuum stability is quite sensitive to the t-quark mass; stability is provided up to Plank-mass scale using αs and mt in a consistent way.
mr: Kniehl, Pikelner, Veretin CPC 206, 84 (2016)
Buttazzo et al., JHEP 12, 089 (2013)
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sa, Moch, Thier PLB 763, 341 (2016)
Electroweak production → reduced impact of αs and the PDF umcertainties HATHOR framework t-channel: NNLO s-channel: NNLO threshold. resum. Different PDFs prefer value of mt(mt) ~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
Brucherseifer, Caola, Melnikov PLB 736, 58 (2014)
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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)
sa, Blümlein, Moch PLB 777, 134 (2018) sa, Blümlein, Kulagin, Moch, Petti hep-ph/1808.06871
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ABMP16 CJ15 CT10 CT14 epWZ16 MMHT14 NPDF 28 21 26 26 14 31 μ0
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9 1.69 1.69 1.69 1.9 1 χ2 4065 4108 4148 4153 4336 4048 PDF shape
xα(1-x)β exp[P(x,ln(x))] xα(1-x)βP(x,√x) xα(1-x)β exp[P(x,√x)] xα(1-x)β exp[P(x,√x)] xα(1-x)βP(x,√x) xα(1-x)βP(x,√x)
Constraints ū=đ (x→0) αuv=αdv αū=αđ=αs ū=đ (x→0) αuv=αdv βuv=βdv αū=αđ=αs αū=αđ=αs ū=đ (x→0) αs(MZ) 0.1153 0.1147 0.1150 0.1160 0.1162 0.1158
Various PDF-shape modifications provide comparable description with NPDF~30 Some deterioration, which happens in cases is apparently due to constraints on large(small)-x exponents Conservative estimate of uncertainty in αs(MZ): 0.0007, more optimistic: 0.0003
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Valence u-quark is modeled by xα(1-x)βNN(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 xα(1-x)βP(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
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αs(MZ)=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) – mc(mc)=1.252±0.018(exp.)-0.01(th.) GeV in nice agreement with
description, while VFN scheme pulls αs up
– the high-twist terms still play important role: larger value of αs if not taken into account – mt(mt)= 160.9± 1.1 GeV
mt(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 αs
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Combination of the threshold corrections (small s), high-energy limit (small x), and the NNLO massive OMEs (large Q2)
Kawamura, Lo Presti, Moch, Vogt NPB 864, 399 (2012)
small s small x large Q2 s ξ=Q2/m2 η=s/4m2-1
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sa, Blümlein, Moch PRD 86, 054009 (2012)
Power-like terms affect comparison even with a “safe” cut W2≥ 12.5 GeV2
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HATHOR (NNLO terms are checked with TOP++)
Langenfeld, Moch, Uwer PRD 80, 054009 (2009) Czakon, Fiedler, Mitov PRL 110, 252004 (2013)
Pole MSbar Running mass definition provides nice perturbative stability
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ABMP16 updated
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Uncertainties explodes if extra PDF parameters are used