lattice “cross-sections” - pion pdfs from pseudo-pdfs and … · 2019-07-17 · j. badier et...
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Lattice “Cross-Sections” - Pion PDFs from Pseudo-PDFs and Pseudo-Structure Functions
Colin EgererIn Collaboration with:R. Sufian, J. Karpie, K. Orginos, J. Qiu, D. RichardsR. Edwards, B. Joo, F. Winter, C. CarlsonA. Radyushkin, S. Zafeiropoulos, T. Khan
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➔ Models not a complete picture
➔ Global analysis techniques not uniquely defined
➔ Not fully known
An Essential Window into Hadronic Structure
2
➔ Essential for interpretation of high-energy scattering data & BSM searches at energy frontier
DIS
Parton Model
PDFs - non-perturbative
pQCD
M. Tanabashi et al. (Particle Data Group), Phys. Rev. D 98, 030001 (2018)
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Pion Structure - Input from LQCD
3
➔ A numerically cheap arena of notable impact
◆ beyond DCSB, long-range interaction◆ nucleon quark sea flavor asymmetry
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Pion Structure - Input from LQCD
3
➔ Chiefly from pionic Drell-Yan
E.g. J. S. Conway et al., Phys. Rev. D 39, 39 (1989)J. Badier et all., Z. Phys. C18, 281 (1983) B. Betev et al., Z. Phys. C28, 9 (1985)
➔ A numerically cheap arena of notable impact
◆ beyond DCSB, long-range interaction◆ nucleon quark sea flavor asymmetry
LO Analysis Conflicts with Expectations
PR12-15-006: TDIS @ JLab(pion structure via Sullivan process)
J. S. Conway et al., Phys. Rev. D 39, 39 (1989)
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Pion Structure - Input from LQCD
3
➔ Chiefly from pionic Drell-Yan
E.g. J. S. Conway et al., Phys. Rev. D 39, 39 (1989)J. Badier et all., Z. Phys. C18, 281 (1983) B. Betev et al., Z. Phys. C28, 9 (1985)
➔ A numerically cheap arena of notable impact
◆ beyond DCSB, long-range interaction◆ nucleon quark sea flavor asymmetry
LO Analysis Conflicts with Expectations
J. S. Conway et al., Phys. Rev. D 39, 39 (1989)
Craig Roberts’ talk @ APS GHP 2019
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Pion Structure - Input from LQCD
3
➔ Chiefly from pionic Drell-Yan
E.g. J. S. Conway et al., Phys. Rev. D 39, 39 (1989)J. Badier et all., Z. Phys. C18, 281 (1983) B. Betev et al., Z. Phys. C28, 9 (1985)
➔ A numerically cheap arena of notable impact
◆ beyond DCSB, long-range interaction◆ nucleon quark sea flavor asymmetry
LO Analysis Conflicts with Expectations
J. S. Conway et al., Phys. Rev. D 39, 39 (1989)Can an LQCD calculation serve as
a discriminator?Craig Roberts’ talk @ APS GHP 2019
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Lattice “Cross Sections” - Two-Current Correlators
4
Y. Q. Ma & J. W. Qiu, Phys. Rev. D 98, no. 7, 074021 (2018), arXiv:1404.6860 [hep-ph]Y. Q. Ma & J. W. Qiu, Phys. Rev. Lett. 120, no. 2, 022003 (2018), arXiv:1709.03018 [hep-ph]
➢ Defining properties:
○ calculable in LQCD with Euclidean time
○ well-defined continuum limit; UV finite
○ share same collinear div. w/ PDFs
➢ Single-hadron matrix elements of renormalized non-local ops.
PDFsPseudo-structure Functions
Hard Coefficients
valid for any finite provided
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Lattice “Cross Sections” - Pseudo-PDFs
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➔ A single-hadron matrix element of a slightly different character
➔ An analogous factorization
Perturbatively computable coefficients&
Ioffe-Time Distributions
T. Izubuchi, et al., Phys.Rev. D98 (2018) no.5, 056004, arXiv: 1801.03917 [hep-ph]A. Radyushkin, Phys.Lett. B781 (2018) 433-442, arXiv: 1710.08813 [hep-ph]J.-H. Zhang, et al., Phys.Rev. D97 (2018) no.7, 074508, arXiv: 1801.03023 [hep-ph]
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Sketch of Pseudo-PDF Lattice Calculations
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➔ Standard 3pt/2pt correlations
➔ Summation method to improve matrix element extraction
➔ Explicit momentum projections at operator insertions
➔ Removal of pure higher-twist piece
C. Bouchard et.al ,Phys. Rev. D 96, no. 1, 014504 (2017)
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Two-Current Correlators - Wick Contractions
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➔ 4pt function with light-quark currents
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Two-Current Correlators - Wick Contractions
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➔ Heavy-light currents
◆ sufficiently small and leading-twist contribution to PDFW. Detmold & C.J. D. Lin, Phys.Rev. D73 (2006) 014501 hep-lat/0507007
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Two-Current Correlators - Wick Contractions
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➔ Heavy-light currents
◆ sufficiently small and leading-twist contribution to PDF
➔ Repeat calculation for varying src/snk separations
W. Detmold & C.J. D. Lin, Phys.Rev. D73 (2006) 014501 hep-lat/0507007
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Two-Current Correlators - Wick Contractions
7
➔ Heavy-light currents
◆ sufficiently small and leading-twist contribution to PDF
➔ Repeat calculation for varying src/snk separations
W. Detmold & C.J. D. Lin, Phys.Rev. D73 (2006) 014501 hep-lat/0507007
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Two-Current Correlators - Wick Contractions
7
➔ Heavy-light currents
◆ sufficiently small and leading-twist contribution to PDF
➔ Repeat calculation for varying src/snk separations
W. Detmold & C.J. D. Lin, Phys.Rev. D73 (2006) 014501 hep-lat/0507007
Momentum smearing for high momenta
G. S. Bali et al. Phys. Rev. D93, 094515 (2016), arXiv:1602.05525 [hep-lat]
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Choice of Currents
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➔ Anti-symmetric vector-axial currents pion
➔ Properly chosen kinematics
➔ Why this combination of currents? Apply factorization
◆ direct access to without contamination
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Ensemble & Typical Ratio Fits
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E1 E1
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Smooth !
Isolation of Distribution Functions
10
➢ Generically proceed from
○ Ioffe-time (Pseudo-) structure fns.
○ Pseudo-structure fns.
➢ Inverse transformations grossly ill-posed
○ Supply additional information
➢ Numerically perform integration
➢ More sophisticated analyses
○ Bayesian reconstructionJ. Karpie, et al. JHEP 1904 (2019) 057 arXiv:1901.05408 [hep-lat] JLAB-THY-19-2898
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Lattice “Cross Sections” and
11
E1❖ 490 configuration ensemble
➢ increasing numbers of sources per momenta
❖ Single determination
❖ not yet quantified
No volume average!R. Sufian, J. Karpie, CE et al., Phys. Rev. D99 (2019) no.7, 074507,
arXiv:1901.03921 [hep-lat]
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Lattice “Cross Sections” and
12
E1
PRELIMINARY
❖ 2560 configuration ensemble
➢ 10 statistically indep. streams
➢ 4 sources per cfg
❖ Numerous determinations
❖ Reduced matrix elements
Volume average!
❖ Evolved to common scale (4 GeV MS)K. Orginos, A. Radyushkin, J. Karpie, and S. Zafeiropoulos, Phys. Rev. D96, 094503 (2017)
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Lattice “Cross Sections” and
13
E1 E1
PRELIMINARY
R. Sufian, J. Karpie, CE et al., Phys. Rev. D99 (2019) no.7, 074507, arXiv:1901.03921 [hep-lat]
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Extracted Valence PDF via Pseudo-PDF
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E1 E1
PRELIMINARY
PRELIMINARY
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Extracted Valence PDF via Two-Currents
15
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Comparison with the Literature
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R. Sufian, J. Karpie, CE et al., Phys. Rev. D99 (2019) no.7, 074507
➔ Appear to be capturing importance of gluonsP. C. Barry et al., Phys. Rev. Lett. 121, 152001 (2018), arXiv:1804.01965 [hep-ph]
➔ Favoring
➔ Consistent w/ NLL threshold soft-gluon resummation effects (ASV)
M. Ding, K. Raya, D. Binosi, L. Chang, C. Roberts, S. Schmidt, arXiv:1905.05208 [nucl-th]
➔
Sea
Glue
Parameter free cont. approach to twovalence-body bound-state problem
Rescaled ASV
➔ Calculation/prediction of 6 Mellin moments
➔
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Outlook
17
➔ PDFs determined experimentally via a global analysis of numerous observables
➔ Calculations of lattice calculable and factorizable matrix elements are encouraging
◆ some systematics unquantified
➔ Statistics limited
➔ PDFs ought to be extracted via a simultaneous analysis of matrix elements
◆ e.g. pPDF, SS, SP, VV, AA, etc.
Discretization effects...
R. Briceño et al., Phys. Rev. D 98, no. 1, 014511 (2018), arXiv:1805.01034 [hep-lat]
G. S. Bali et al., Phys. Rev. D 98, no. 9, 094507 (2018), arXiv:1807.06671 [hep-lat]G. S. Bali et al., Eur. Phys. J. C78 (2018) no. 3, 217, arXiv:1709.04325 [hep-lat]
Finite volume effects...
Log. corrections &
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THANK YOU!
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More on quasi/pseudo-distributions
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X. Ji, Phys. Rev. Lett. 110, 262002 (2013), arXiv:1305.1539 [hep-ph]
K. Orginos, A. Radyushkin, J. Karpie, and S. Zafeiropoulos, Phys. Rev. D96, 094503 (2017), arXiv:1706.05373 [hep-ph]
Fourier transform over length of Wilson line
Fourier transform Ioffe time - fixed length Wilson line
K. Cichy & M. Constantinou, arXiv:1811.07248v1 [hep-lat]
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Leading Order Coefficient Functions - Coordinate Space
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Matching Kernels & the Pion Valence Distribution
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➔ Factorized relation asymptotic parton state order-by-order in
➔ To ensure access to valence distribution◆ momentum space pseudo-structure fns.
Y. Q. Ma & J. W. Qiu, Phys. Rev. Lett. 120, no. 2, 022003 (2018), arXiv:1709.03018 [hep-ph]
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Higher-Twist Effects?
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