Boer-Mulders effect in the unpolarized pion induced Drell–Yan process at COMPASS within TMD factorization

Wang, Xiaoyu; Mao, Wenjuan; Lü, Zhun

doi:10.1140/epjc/s10052-018-6114-4

“…The The W (0) 2,5 contribution, which corresponds to the cos(2ϕ) and sin(2ϕ) angular modulations of the cross section, are proportional to a (weighted) convolution of two Boer-Mulders functions h ⊥ 1 in the transverse plane [141][142][143], where h ⊥ 1a measures the net transverse polarization of flavor a, longitudinal momentum fraction x, and given transverse momentum k T within an unpolarized proton [144]. It does not match onto leading twist-2 collinear PDFs, i.e., for Λ QCD q T , each h ⊥ 1 is suppressed by at least one power of Λ QCD /q T [145] relative to the leading-power beam functions B a in W −1,4 , which do match onto leading twist-2 PDFs.…”

Section: Generic Fiducial Power Correctionsmentioning

confidence: 99%

Drell-Yan qT resummation of fiducial power corrections at N3LL

Ebert

¹

,

Michel

²

,

Stewart

³

et al. 2021

J. High Energ. Phys.

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We consider Drell-Yan production pp → V*X → LX at small qT ≪ Q, where qT and Q are the total transverse momentum and invariant mass of the leptonic final state L. Experimental measurements require fiducial cuts on L, which in general introduce enhanced, linear power corrections in qT/Q. We show that they can be unambiguously predicted from factorization, and resummed to the same order as the leading-power contribution. For the fiducial qT spectrum, they constitute the complete linear power corrections. We thus obtain predictions for the fiducial qT spectrum to N3LL and next-to-leading-power in qT/Q. Matching to full NNLO ($$ {\alpha}_s^2 $$ α s 2 ), we find that the linear power corrections are indeed the dominant ones, and once included by factorization, the remaining fixed-order corrections become almost negligible below qT ≲ 40 GeV. We also discuss the implications for more complicated observables, and provide predictions for the fiducial ϕ* spectrum at N3LL+NNLO. We find excellent agreement with ATLAS and CMS measurements of qT and ϕ*. We also consider the $$ {p}_T^{\mathrm{\ell}} $$ p T ℓ spectrum. We show that it develops leptonic power corrections in qT/(Q − 2$$ {p}_T^{\mathrm{\ell}} $$ p T ℓ ), which diverge near the Jacobian peak $$ {p}_T^{\mathrm{\ell}} $$ p T ℓ ∼ Q/2 and must be kept to all powers to obtain a meaningful result there. Doing so, we obtain for the first time an analytically resummed result for the $$ {p}_T^{\mathrm{\ell}} $$ p T ℓ spectrum around the Jacobian peak at N3LL+NNLO. Our method is based on performing a complete tensor decomposition for hadronic and leptonic tensors. We show that in practice this is equivalent to often-used recoil prescriptions, for which our results now provide rigorous, formal justification. Our tensor decomposition yields nine Lorentz-scalar hadronic structure functions, which for Z/γ* → ℓℓ or W → ℓν directly map onto the commonly used angular coefficients, but also holds for arbitrary leptonic final states. In particular, for suitably defined Born-projected leptons it still yields a LO-like angular decomposition even when including QED final-state radiation. Finally, we also discuss the application to qT subtractions. Including the unambiguously predicted fiducial power corrections significantly improves their performance, and in particular makes them applicable near kinematic edges where they otherwise break down due to large leptonic power corrections.

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“…For completeness we remark that the importance of TMD evolution for the description of pion-induced DY and the recent COMPASS data was also studied in refs. [73,[97][98][99][100][101].…”

Section: Jhep02(2021)166mentioning

confidence: 99%

The Drell-Yan process with pions and polarized nucleons

Bastami

¹

,

Parsamyan

²

,

Pasquini

³

et al. 2021

J. High Energ. Phys.

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The Drell-Yan process provides important information on the internal struc- ture of hadrons including transverse momentum dependent parton distribution functions (TMDs). In this work we present calculations for all leading twist structure functions de- scribing the pion induced Drell-Yan process. The non-perturbative input for the TMDs is taken from the light-front constituent quark model, the spectator model, and available parametrizations of TMDs extracted from the experimental data. TMD evolution is im- plemented at Next-to-Leading Logarithmic precision for the first time for all asymmetries. Our results are compatible with the first experimental information, help to interpret the data from ongoing experiments, and will allow one to quantitatively assess the models in future when more precise data will become available.

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“…Feynman-x or x F , is a variable of interest that sheds light on the longitudinal structure of the initial state of the interacting quark. The solid blue line represents the model calculated results, and the dashed red line represents the fitted PDF calculated results [17] to obtain the proton Boer-Mulders distribution function and Eq. ( 23) to obtain the proton TMD PDFs.…”

Section: Resultsmentioning

confidence: 99%

“…To calculate the asymmetries in Eqs. (16) and (17) we need first of all the first moment of pion Boer-Mulders function, h…”

Section: The Pion Boer-mulders Functionmentioning

confidence: 99%

Boer–Mulders function of the pion and pretzelosity distribution of the proton in the polarized pion-proton Drell–Yan process at COMPASS

Liu

¹

,

Ma

²

2021

Eur. Phys. J. C

1

0

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We present a phenomenological analysis of the $$q_{\text {T}}$$ q T -weighted transverse spin dependent azimuthal asymmetry recently measured by the COMPASS Collaboration in polarized pion-proton Drell–Yan process. In the kinematical regimes explored by experiments, we consider the leading-twist contributions from the Boer–Mulders distribution functions $$h_{1}^{\perp }(x,k_{\text {T}}^{2})$$ h 1 ⊥ ( x , k T 2 ) of both the pion and the proton, the transversity distribution $$h_{1}(x,k_{\text {T}}^{2})$$ h 1 ( x , k T 2 ) and the pretzelosity distribution $$h_{1\text {T}}^{\perp }(x,k_{\text {T}}^{2})$$ h 1 T ⊥ ( x , k T 2 ) of the proton, with the unpolarized transverse-momentum-dependent distribution function $$f_{1}(x,k_{\text {T}}^{2})$$ f 1 ( x , k T 2 ) of the proton being also involved in the calculation. By comparing the data reported by the COMPASS Collaboration with theoretical calculated results, we find that the COMPASS measurements represent the first experimental evidence of the Boer–Mulders effect in polarized Drell–Yan process. We also test the universality between proton and pion Boer–Mulders functions.

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Boer-Mulders effect in the unpolarized pion induced Drell–Yan process at COMPASS within TMD factorization

Cited by 16 publications

References 124 publications

Drell-Yan qT resummation of fiducial power corrections at N3LL

Drell-Yan qT resummation of fiducial power corrections at N3LL

The Drell-Yan process with pions and polarized nucleons

Boer–Mulders function of the pion and pretzelosity distribution of the proton in the polarized pion-proton Drell–Yan process at COMPASS

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