Measurement of $\mathbf{q_T}$-weighted transverse-spin-dependent azimuthal asymmetries at COMPASS

Riccardo Longo

REVIEW 3 major objections 4 minor 21 references

Measurement of $\mathbf{q_T}$-weighted transverse-spin-dependent azimuthal asymmetries at COMPASS

T0 review · 3 major / 4 minor · reviewed 2026-08-14 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗ Review JSON

Pith's one-line read First data extraction of the pion Boer-Mulders function from Drell-Yan spin asymmetries.

desk verdict A clean, honest preliminary COMPASS status report; the one new physics claim, the first pion Boer-Mulders extraction, is real but rides on untested zero-sea assumptions. read the letter →

arxiv 1908.03310 v1 pith:LOC6QTTP submitted 2019-08-09 hep-ex hep-ph

Riccardo Longo This is my paper · ORCID

classification hep-exhep-ph

keywords Drell-Yantransverse-spinasymmetriesqT-weightedBoer-MuldersfunctionSiversTMDPDFsCOMPASSsemi-inclusivedeepinelasticscattering

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper reports the first extraction of the first transverse moment of the pion Boer-Mulders function from data, using the $q_T$-weighted transverse-spin asymmetry $A^{\sin(2\phi-\phi_S) q_T/M_\pi}_T$ measured in COMPASS Drell-Yan scattering of a 190 GeV/$c$ $\pi^-$ beam on a transversely polarized proton target. In the TMD approach, weighted asymmetries turn convolutions of TMD parton distributions into products of their transverse moments, which is what allows the Boer-Mulders moment to be solved for directly. The paper also compares the $q_T$-weighted Sivers asymmetry in Drell-Yan with a projection from SIDIS data that assumes the predicted sign change of the Sivers function. This matters because the pion Boer-Mulders function is a time-reversal-odd transverse-momentum-dependent distribution that had previously been constrained only by models; a direct data point gives the TMD program a new anchor.

What carries the argument

The machinery is the $q_T$-weighted transverse-spin asymmetry itself: a ratio of a $q_T$-weighted integral of a spin-dependent structure function to the unweighted integrated unpolarized structure function. The weight is chosen so the convolution over the two intrinsic quark transverse momenta collapses into a product of transverse moments of TMD PDFs; for the Boer-Mulders channel, Eq. (1.4) expresses the $q_T/M_\pi$-weighted asymmetry as the product of the pion Boer-Mulders first moment and the proton transversity, divided by the unpolarized flavor-sum denominator. Inserting the proton transversity from a point-by-point extraction, unpolarized PDFs, and a valence pion PDF leaves the Boer-Mulders moment as the only unknown, read off bin by bin in $x_\pi$. The asymmetries are extracted with the modified double-ratio method, which cancels most acceptance effects.

What would settle it

Include non-zero sea-quark transversity and sea-quark Boer-Mulders terms in the analysis of the same COMPASS data and see whether the extracted pion Boer-Mulders moment moves by more than the quoted uncertainty; alternatively, measure the same $q_T$-weighted asymmetry in $\pi^+ p$ Drell-Yan, where the sea-quark terms enter with different charge and flavor weights, and check whether the resulting $h^{\perp(1)}_{1,\pi}$ is consistent with the $\pi^-$ result.

Watch

Extended reading notes

Core claim

Combining the full 2015 Drell-Yan data set with about half of the 2018 data, the collaboration extracts the three $q_T$-weighted transverse-spin asymmetries in the high-mass range $M_{\mu\mu}\in[4.3,8.5]$ GeV/$c^2$. The central new result is the first data extraction of $x_\pi h^{\perp(1)\bar{u}}_{1,\pi}(x_\pi)$, the first transverse moment of the valence anti-up quark Boer-Mulders distribution of the pion, obtained by rewriting the weighted asymmetry $A^{\sin(2\phi-\phi_S) q_T/M_\pi}_T$ as a product of this moment with the proton transversity distribution and dividing out the latter. The extraction sets sea-quark Boer-Mulders and sea-quark transversity terms to zero and keeps only u, d, and s contributions in the denominator. The quoted values in Fig. 4b are compared with an existing parametrization. The $q_T$-weighted Sivers Drell-Yan asymmetry measured on the same samples is consistent, within current statistical precision, with the SIDIS-based projection that assumes the Sivers sign change, though the precision does not yet allow a conclusion on that hypothesis.

Load-bearing premise

The load-bearing assumption is that sea quarks contribute nothing to the asymmetry used for the Boer-Mulders extraction; if sea-quark transversity or sea-quark Boer-Mulders effects are non-negligible at COMPASS kinematics, the extracted value is biased.

Editorial extensions

If this is right

The pion Boer-Mulders moment now has a data point that model calculations and global fits must reproduce, turning a previously model-only quantity into an observable constraint.
The same weighting technique can be applied to the other modulations in Eq. (1.1), giving access to other transverse moments of pion and nucleon TMDs without assuming a functional form for the $k_T$ dependence.
When the remaining half of the 2018 data is added, the statistical uncertainty on both the Sivers comparison and the Boer-Mulders point will shrink; if the Sivers comparison then shows the sign pattern predicted from SIDIS with high significance, that would support the sign-change hypothesis.
The measured $q_T$-weighted Sivers asymmetry provides a scale-matched counterpart to the SIDIS weighted Sivers measurement, making the comparison less sensitive to modeling assumptions than standard asymmetries.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

Because the extraction drops sea-quark transversity and Boer-Mulders terms, a natural follow-up is a global fit that includes those sea-quark TMDs and checks whether the valence Boer-Mulders point moves; that is an extension beyond the paper's assumption, not something the paper performs.
The same $q_T$-weighting procedure could be applied to $\pi^+$ or kaon beams to separate valence flavors; the pattern of the $x_\pi$ dependence of the Boer-Mulders moment across flavors would discriminate between model predictions more sharply than a single beam.
Feeding the extracted pion Boer-Mulders moment into a prediction for the $\cos 2\phi$ asymmetry in unpolarized $\pi^- p$ Drell-Yan, following Ref. [7] of the paper, would test the TMD against a target-polarization-free observable.

Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

The short version: this is a preliminary COMPASS proceedings note that adds about half of the 2018 Drell-Yan data to the qT-weighted asymmetries already reported for 2015. The genuinely new item is the extraction of the first transverse moment of the pion Boer-Mulders function in Fig. 4b. The Sivers comparison is an update, not a new result.

What the paper does well: the analysis follows the modified double-ratio method used for the 2015 data, the presentation is clear, and the authors state their assumptions openly. They explicitly say the Sivers sign-change test is not yet conclusive, and the systematic band is shown. That is honest. The new BM extraction is presented as an independent estimate, and the comparison with Boer's parametrization is a reasonable first look.

The soft spots are real. The BM extraction assumes zero sea-quark Boer-Mulders and transversity. That is not a harmless convention: the measured asymmetry is a flavor sum, and those dropped terms enter with their own weights. The paper provides no estimate or upper bound, so the result in Fig. 4b is model-dependent rather than a direct measurement. The same section neglects Q2 evolution of the input transversity TMD and neglects PDF uncertainties. Those are acknowledged in the text, but not quantified. The normalization uncertainties from target polarization and dilution factor (5% and 8%) are omitted from the plots; for a weighted asymmetry they may partly cancel, but the reader cannot tell. The Sivers comparison in Fig. 4a is too low-statistics to constrain the sign-change hypothesis; the paper says so.

None of this makes the paper wrong. It makes the central new claim exploratory. The assumptions could bias the extraction if sea-quark TMDs are non-negligible; the stress-test concern is on target. A revised version that gives a model-based estimate of the dropped terms, or at least a scan over plausible sea-quark sizes, would materially improve it. The 2015+2018 combined asymmetries are useful to the COMPASS TMD community as a status report.

Who this is for: people tracking the TMD program at COMPASS, and those interested in the pion Boer-Mulders function. It is not a definitive result. I would send it to a referee if it were submitted as a regular paper, because the data and extraction deserve scrutiny; the referee should push for a quantitative treatment of the sea-quark assumption and scale dependence. As a proceedings note, it is fine.

Referee Report

3 major / 4 minor

Summary. The paper reports preliminary COMPASS measurements of qT-weighted transverse-spin-dependent azimuthal asymmetries in π−p↑ Drell-Yan, combining the full 2015 data set with about 50% of the 2018 data in the high-mass range M_μμ ∈ [4.3,8.5] GeV/c². Three weighted asymmetries are extracted as functions of x_N, x_π, x_F, and M using the modified double-ratio method. The sin ϕS asymmetry is compared with a projection from COMPASS SIDIS under the sign-change hypothesis for the Sivers function, and the sin(2ϕ−ϕS) asymmetry is used, together with external unpolarized PDFs and a previous COMPASS transversity extraction, to obtain the first transverse moment of the valence pion Boer-Mulders distribution h_1^{⊥(1)\bar u}_{1,π}(xπ). The central claim is this first extraction, shown in Fig. 4b.

Significance. If the extraction is robust, the pion Boer-Mulders transverse moment is genuinely new experimental information, because the qT-weighted method avoids assumptions on the kT shape of TMDs. The paper also provides a useful, if not yet conclusive, test of the Sivers sign-change hypothesis; the authors appropriately state that the present significance is insufficient to draw conclusions. Strengths include the use of the modified double-ratio method, the inclusion of false-asymmetry systematic studies, and the combination of two data-taking periods. The reliability of the central claim, however, hinges on the approximations in Eq. (3.2) and on the completeness of the quoted uncertainties, both of which need quantitative support before the 'first extraction' statement can be taken at face value.

major comments (3)

[Section 3.2, Eq. (3.2)] The assumption that Boer-Mulders and transversity PDFs of sea quarks are zero is load-bearing and has no quantitative justification. The measured asymmetry is a charge-weighted flavour sum: any nonzero sea-quark Boer-Mulders function of the pion or sea transversity of the proton contributes additively to the numerator of Eq. (3.2) before the ratio is inverted, while the denominator keeps the full unpolarized u, d, s sea. The valence-region argument used for the Sivers projection in Section 3.1 therefore does not apply to the dropped terms in the same way. Please provide a model-based estimate, an upper bound, or a sensitivity test quantifying the bias on each extracted point of xπ h_1^{⊥(1)\bar u}_{1,π} in Fig. 4b, or explicitly present the result as conditional on the sea-quark-zero approximation.
[Section 3.2, Fig. 4b] The text states that the hard-scale dependence of the transversity TMD PDF is neglected, while the input transversity h_1^{u,p} comes from a point-by-point extraction from COMPASS SIDIS data and is applied to DY data at M_μμ ∈ [4.3,8.5] GeV/c². No estimate of the scale mismatch is given, even though transversity evolution is not expected to be negligible in this range. The same paragraph also states that uncertainties on the unpolarized proton and pion PDFs are neglected. Please quantify the Q2-evolution effect and the PDF-uncertainty effect, or show that they are small compared with the quoted statistical and asymmetry systematic errors.
[Figures 3 and 4] The figures show statistical and, in Fig. 4b, combined statististical-plus-systematic error bars, but the caption of Fig. 3 states that normalization uncertainties from target polarization (5%) and dilution factor (8%) are not shown. Since these are not automatically expected to cancel in the ratio defining the Boer-Mulders moment, the paper should either demonstrate the cancellation explicitly or include the normalization uncertainty in the error budget of the central extraction. Without this, comparisons with the parametrization of Ref. [21] in Fig. 4b are incomplete.

minor comments (4)

[Section 3.2, abstract] The phrase 'was never extracted before' is a strong novelty claim. Since the comparison in Fig. 4b is with a parametrization rather than with a previous data-based extraction, please define what qualifies as an extraction and cite all prior phenomenological determinations of the pion Boer-Mulders function (e.g., from unpolarized cos 2ϕ Drell-Yan analyses and model fits) so that the novelty statement is verifiable.
[Eqs. (1.4), (3.2), and surrounding text] The notation for the azimuthal angle is inconsistent: Eq. (1.4) uses sin(2ϕ−ϕS), Eq. (3.2) and Fig. 3 use sin(2φ−ϕS) or sin(2φ−φS), and the text mixes φ and ϕ. Please unify the symbol for the lepton azimuthal angle throughout.
[Fig. 4b] The curve from Ref. [21] is shown as a line without uncertainty or a statement of whether it is a model prediction or a fit to other data; please clarify its status in the caption or text.
[Title page] The displayed title contains 'COMP ASS' due to a line-break artifact; the correct spelling should be restored in the final version.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the qT-weighted asymmetries are measured directly, and the Boer-Mulders extraction solves Eq. (3.2) for an unknown quantity using external PDFs and a transversity input from a different observable.

full rationale

The derivation chain is not circular. The qT-weighted TSAs are measured directly from COMPASS 2015 and 2018 Drell-Yan data in Section 2. In Section 3.1, the SIDIS-based projection is constructed by taking the first kT^2-moment of the Sivers function from a separate COMPASS SIDIS measurement [8] and inserting it into Eq. (3.1); the DY measurement is then compared with that projection, so the predicted DY asymmetry is not used as its own input. In Section 3.2, Eq. (3.2) is an inversion of the measured A^{sin(2φ-φS) qT/Mπ}_T asymmetry: the paper solves for h^{⊥(1)\bar u}_{1,π} using external unpolarized PDFs (CTEQ5D, GRV-PI), a transversity extraction from SIDIS data [20], and the measured asymmetry. The Boer-Mulders moment is not fitted from the same asymmetry and then relabeled as a prediction; it is the unknown being extracted. The reuse of COMPASS-related results is limited to SIDIS observations of different observables, so those inputs are independent of the Drell-Yan asymmetry being analyzed and do not create a definitional tautology. The assumption that sea-quark Boer-Mulders and transversity contributions vanish is an untested model assumption that could bias the central value, but it is not circular because the dropped terms are not secretly reintroduced as the extracted quantity. The final comparison with the D. Boer parametrization provides an external benchmark, further supporting the independence of the extraction.

Assumptions & free parameters 1 free parameters · 7 assumptions · 0 invented entities

The paper introduces no new free parameters or entities. Its central extraction rests on a chain of external inputs (PDFs, prior transversity extraction, SIDIS Sivers parametrization) and on simplifying assumptions about sea-quark TMDs and Q2 evolution, which are stated but not validated within this work.

free parameters (1)

Sivers x-dependence parameters a_q, b_q, c_q = from Ref. [8] (not quoted here)
Used in Eq. (3.1) to project the DY Sivers asymmetry from SIDIS data; these parameters were fitted to SIDIS data in prior work, not in this paper.

assumptions (7)

domain assumption TMD factorization and the leading-twist Drell-Yan cross-section expression in Eq. (1.1) are valid.
Invoked at the start of Section 1 via Refs. [1] and [13] to define the structure functions and TSAs.
ad hoc to paper Sea quark contributions are negligible in the Sivers projection, so only the u valence quark contributes.
Stated in Section 3.1, justified by the valence region coverage shown in Fig. 2a, but not quantitatively checked.
domain assumption The Sivers function changes sign between SIDIS and Drell-Yan, as predicted by QCD.
Assumed in Eq. (3.1) and Ref. [16] when projecting the SIDIS result to the DY case.
ad hoc to paper Sea quark Boer-Mulders and transversity contributions are zero, and only u, d, s quarks appear in the denominator of Eq. (3.2).
Stated in Section 3.2 after Eq. (3.2); this assumption is load-bearing for the pion Boer-Mulders extraction.
domain assumption Q2 evolution effects between the SIDIS and DY measurements and within the BM extraction are neglected.
Explicitly noted in Sections 3.1 and 3.2; the hard scales differ, and no evolution kernel is applied.
domain assumption The unpolarized proton PDFs (CTEQ5D) and pion PDFs (GRV-PI) at Q2 = 25 (GeV/c)2 are reliable inputs.
Used in Eqs. (3.1) and (3.2) via Refs. [14,17,18]; their uncertainties are neglected in the final result.
domain assumption The proton transversity distribution from the point-by-point extraction in Ref. [20] is valid and can be used as an input.
Used directly in Eq. (3.2); the paper does not propagate any uncertainty from this input beyond the quoted statistical component.

how reviews work

0 comments

Cite this review

Pith. "Pith review of Measurement of $\mathbf{q_T}$-weighted transverse-spin-dependent azimuthal asymmetries at COMPASS." pith.science (2026). https://pith.science/paper/LOC6QTTP

@misc{pith2026190803310,
  author       = {Pith},
  title        = {Pith review of: Measurement of $\mathbfq_T$-weighted transverse-spin-dependent azimuthal asymmetries at COMPASS},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/LOC6QTTP}},
  note         = {Machine review of arXiv:1908.03310}
}

abstract

COMPASS is a fixed-target experiment in operation at the CERN North Area (SPS, M2 beam-line) since 2002. An important part of the broad physics programme of the experiment is dedicated to the exploration of the transverse spin-structure of the nucleon studying target transverse spin dependent azimuthal asymmetries (TSAs) arising in the Semi-Inclusive DIS (SIDIS) and Drell-Yan (DY) cross-sections. In addition to those measurements, COMPASS has recently studied also the TSAs weighted by powers of the hadron transverse momentum (in SIDIS) and virtual photon transverse momentum, $q_T$ (in DY). In the transverse momentum dependent (TMD) QCD approach, the conventional DY TSAs are interpreted as convolutions of the beam pion and of the transversely polarized target proton TMD parton distribution functions (PDFs), while the $q_T$-weighted TSAs can be interpreted as simple products of transverse moments of the TMD PDFs. In 2015 and 2018 COMPASS performed two years of Drell-Yan data taking with a 190 GeV/$c$ $\pi^-$ beam impinging on a transversely polarized NH$_3$ target. The analysis of the $q_T$-weighted TSAs performed on these two data sets is presented in this paper. The results for DY Sivers $q_T$ weighted TSA are compared with the expectations based on the studies of the weighted Sivers asymmetry measured in the SIDIS process. Combining the information from SIDIS and DY measurements, the pion Boer-Mulders TMD PDF is also studied.

Figures

Figures reproduced from arXiv: 1908.03310 by the authors.

**Figure 2.** xN versus xπ (a) and qT (b) distributions in the HM range from NH3, 2018 data. can be found in [9]. The 23 weeks of data-taking were divided in 9 periods, each consisting of consecutive weeks with opposite target polarizations. In this Letter, only ∼50% of the available 2018 data have been analyzed. Contrary to the standard TSAs analysis, no cut on qT is applied since the integration over the full qT range, where th… view at source ↗

**Figure 3.** The qT-weighted TSAs obtained combining the whole 2015 data set with ∼ 50% of 2018 data set. The systematic uncertainties are represented by the blue bands. Normalization uncertainties from target polarization (5 %) and dilution factor calculation (8 %) are not shown. The projection to the DY case is obtained using Eq. (1.3) and assuming no contribution of the sea quarks in the flavour sums, and the sign-change of t… view at source ↗

Figures from the paper (1 more)

**Figure 4.** Figure 4: (a) The weighted Sivers asymmetry extracted from COMPASS 2015 and 2018 ( [PITH_FULL_IMAGE:figures/full_fig_p006_4.png]

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

21 extracted references · 11 canonical work pages

[21]

Boer, Investigating the origins of transverse spin asymmetries at RHIC , Phys

D. Boer, Investigating the origins of transverse spin asymmetries at RHIC , Phys. Rev. D 60 (1999) 014012 [hep-ph/9902255]. 6

arXiv 1999
[1]

Collins, F oundations of perturbative QCD, Camb

J. Collins, F oundations of perturbative QCD, Camb. Monogr. Part. Phys. Nucl. Phys. Cosmol. 32 (2011) 1

work page 2011
[2]

A. M. Kotzinian and P. J. Mulders, Longitudinal quark polarization in transversely polarized nucleons, Phys. Rev. D54 (1996) 1229 [hep-ph/9511420]

arXiv 1996
[3]

Boer and P

D. Boer and P. J. Mulders, Time reversal odd distribution functions in leptoproduction, Phys. Rev. D57 (1998) 5780 [hep-ph/9711485]

arXiv 1998
[4]

A. V . Efremov et al., Sivers effect in semi-inclusive DIS and in the Drell-Yan process , Phys. Lett. B 612, 233 (2005) [hep-ph/0412353] . 5 Measurement of qT -weighted TSAs at COMPASS Riccardo Longo

work page Pith review arXiv 2005
[5]

Direct extraction of transversity and its accompanying T-odd distribution from the unpolarized and single-polarized Drell-Yan processes

A. Sissakian et al., Direct extraction of transversity and its accompanying T-odd distribution from the unpolarized and single-polarized Drell-Yan process, Phys. Rev. D 72 (2005) 054027 [hep-ph/0505214]

work page Pith review arXiv 2005
[6]

Transversity and its accompanying T-odd distribution from Drell-Yan processes with pion-proton collisions

A. Sissakian et al., Transversity and its accompanying T-odd distribution from Drell–Yan processes with pion-proton collisions, Eur . Phys. J.C46 (2006) 147 [hep-ph/0512095]

work page Pith review arXiv 2006
[7]

Z. Wang, X. Wang and Z. Lu, Boer-Mulders function of pion meson and q T -weighted cos2 φ asymmetry in the unpolarized π− p Drell-Yan at COMPASS, Phys. Rev. D95 (2017) 094004 [1702.03637]

work page Pith review arXiv 2017

Show all 21 references

[8]

COMPASS Collaboration, M. G. Alexeev et al. , Measurement of PT -weighted Sivers asymmetries in leptoproduction of hadrons, Nucl. Phys. B 940 (2019) 34. [hep-ex]

2019
[9]

Parsamyan [COMPASS Collaboration], Transversely polarized Drell-Yan measurements at COMPASS, PoS DIS 2019 (2019) 195

B. Parsamyan [COMPASS Collaboration], Transversely polarized Drell-Yan measurements at COMPASS, PoS DIS 2019 (2019) 195

2019
[10]

Aghasyan et al., First measurement of transverse-spin-dependent azimuthal asymmetries in the Drell-Yan process, Phys

COMPASS collaboration, M. Aghasyan et al., First measurement of transverse-spin-dependent azimuthal asymmetries in the Drell-Yan process, Phys. Rev. Lett. 119 (2017) 112002 [1704.00488]

2017 arXiv
[11]

COMPASS collaboration, J. Matoušek, Measurement of qT -weighted TSAs in 2015 COMPASS Drell–Yan data, in 17th Workshop on High Energy Spin Physics (DSPIN-17), Dubna, Russia, September 11-15, 2017, vol.~938 of J. Phys. Conf. Ser., p.~012012, 2017 [1710.06497], DOI

2015 arXiv
[12]

Matoušek [COMPASS Collaboration], Weighted transverse spin asymmetries in 2015 COMPASS Drell-Yan data, [1812.08505 [hep-ex]]

J. Matoušek [COMPASS Collaboration], Weighted transverse spin asymmetries in 2015 COMPASS Drell-Yan data, [1812.08505 [hep-ex]]

2015 arXiv
[13]

Arnold, A

S. Arnold, A. Metz and M. Schlegel, Dilepton production from polarized hadron hadron collisions, Phys. Rev. D 79 (2009) 034005 [0809.2262 [hep-ph]]

2009 arXiv
[14]

CTEQ collaboration, H. L. Lai, J. Huston, S. Kuhlmann, J. Morﬁn, F. I. Olness, J. F. Owens et al., Global QCD analysis of parton structure of the nucleon: CTEQ5 parton distributions , Eur . Phys. J. C12 (2000) 375 [hep-ph/9903282]

2000 arXiv
[15]

de Florian, R

D. de Florian, R. Sassot and M. Stratmann, Global analysis of fragmentation functions for pions and kaons and their uncertainties , Phys. Rev. D75 (2007) 114010 [hep-ph/0703242]

2007 arXiv
[16]

J. C. Collins, Leading twist single transverse-spin asymmetries: Drell–Yan and deep inelastic scattering, Phys. Lett. B536 (2002) 43 [hep-ph/0204004]

2002 arXiv
[17]

Glück, E

M. Glück, E. Reya and A. V ogt, Pionic parton distributions, Z. Phys. C53 (1992) 651

1992
[18]

Buckley, J

A. Buckley, J. Ferrando, S. Lloyd, K. Nordström, B. Page, M. Rüfenacht et al., LHAPDF6: parton density access in the LHC precision era , Eur . Phys. J.C75 (2015) 132 [1412.7420]

2015 arXiv
[19]

Martin, F

A. Martin, F. Bradamante and V . Barone,Point-by-point extraction of parton distribution functions from SIDIS single transverse-spin asymmetries , 1702.01038 [hep-ph]

arXiv
[20]

Martin, F

A. Martin, F. Bradamante and V . Barone,Extracting the transversity distributions from single-hadron and dihadron production, Phys. Rev. D 91 (2015) no.1, 014034 [1412.5946 [hep-ph]]

2015 arXiv

Pith tools

Reviewed August 14, 2026 · model on record in the stance chip above.

[1] [21]

Boer, Investigating the origins of transverse spin asymmetries at RHIC , Phys

D. Boer, Investigating the origins of transverse spin asymmetries at RHIC , Phys. Rev. D 60 (1999) 014012 [hep-ph/9902255]. 6

arXiv 1999

[2] [1]

Collins, F oundations of perturbative QCD, Camb

J. Collins, F oundations of perturbative QCD, Camb. Monogr. Part. Phys. Nucl. Phys. Cosmol. 32 (2011) 1

work page 2011

[3] [2]

A. M. Kotzinian and P. J. Mulders, Longitudinal quark polarization in transversely polarized nucleons, Phys. Rev. D54 (1996) 1229 [hep-ph/9511420]

arXiv 1996

[4] [3]

Boer and P

D. Boer and P. J. Mulders, Time reversal odd distribution functions in leptoproduction, Phys. Rev. D57 (1998) 5780 [hep-ph/9711485]

arXiv 1998

[5] [4]

A. V . Efremov et al., Sivers effect in semi-inclusive DIS and in the Drell-Yan process , Phys. Lett. B 612, 233 (2005) [hep-ph/0412353] . 5 Measurement of qT -weighted TSAs at COMPASS Riccardo Longo

work page Pith review arXiv 2005

[6] [5]

Direct extraction of transversity and its accompanying T-odd distribution from the unpolarized and single-polarized Drell-Yan processes

A. Sissakian et al., Direct extraction of transversity and its accompanying T-odd distribution from the unpolarized and single-polarized Drell-Yan process, Phys. Rev. D 72 (2005) 054027 [hep-ph/0505214]

work page Pith review arXiv 2005

[7] [6]

Transversity and its accompanying T-odd distribution from Drell-Yan processes with pion-proton collisions

A. Sissakian et al., Transversity and its accompanying T-odd distribution from Drell–Yan processes with pion-proton collisions, Eur . Phys. J.C46 (2006) 147 [hep-ph/0512095]

work page Pith review arXiv 2006

[8] [7]

Z. Wang, X. Wang and Z. Lu, Boer-Mulders function of pion meson and q T -weighted cos2 φ asymmetry in the unpolarized π− p Drell-Yan at COMPASS, Phys. Rev. D95 (2017) 094004 [1702.03637]

work page Pith review arXiv 2017