TMDe2015 - A path towards TMD extraction

Europe/Rome
Giambiagi Lecture Hall (Trieste)

Giambiagi Lecture Hall

Trieste

Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
Andrea Bressan (Universita e INFN, Trieste (IT)), Anna Martin (Trieste University and INFN (IT)), Franco Bradamante (Universita e INFN, Trieste (IT))
Description

Transverse momentum dependent parton distribution functions (TMD PDFs) are crucial elements for the understanding of the nucleon structure in terms of the quark and gluon degrees of freedom in QCD, beyond the collinear approximation. The recent findings in the theoretical and experimental fields have allowed remarkable progress. The knowledge of these functions, however, is still in its infancy. 

This mini-workshop is focused on transversity and TMD extraction from semi-inclusive deep inelastic scattering (SIDIS) data. It is structured as a working group meeting, gathering people directly involved in the field, with the goal of tracking the road towards further progress using the existing data and planning new measurements in the near future. 

The aim of the Italian community involved in the organization is to create an opportunity for deep, open and constructive discussions to review the state of the art and the near future perspectives on

  • TMD evolution and higher twist effects
  • analysis of unpolarised SIDIS data, pT distributions, azimuthal dependences
  • azimuthal asymmetries in transversely and longitudinally polarized SIDIS
  • TMD fragmentation functions in e+e- and SIDIS processes
  • new data analysis methods

with focus on TMD extraction.

The participants, all physicists working on TMD phenomenology and on related experiments, are expected to share their experience, discuss methodologies and propose new ideas with a collaborative attitude in a relaxing environment.
The mini-workshop will mainly consist of round table discussions with a few introductory presentations.

The proceedings will be replaced by a short written report on the outcome of the meeting.

The Workshop is supported by ECSAC, the European Centre for Science Arts and Culture which organizes conferences and meetings in Losinj or Trieste each year since 2001, and it is a hosted activity of the Abdul Salam International Centre for Theoretical Physics.


For any information please contact the Organizing Committee:    e-mail: ecsac@ictp.it

Scientific Programme
Participants
  • Adam Szabelski
  • Albi Kerbizi
  • Alessandro Bacchetta
  • Andrea Bianconi
  • Andrea Bressan
  • Andrea Giovannini
  • Andrea Signori
  • Anna Martin
  • Anselm Vossen
  • Aram Kotzinian
  • Barbara Pasquini
  • Bo-Qiang Ma
  • Charlotte Van Hulse
  • Christian Weiss
  • Cristian Pisano
  • Elena Santopinto
  • Elke-Caroline Aschenauer
  • Fabio Anulli
  • Federico Alberto Ceccopieri
  • Francesco Murgia
  • Franco Bradamante
  • Fulvio Tessarotto
  • Gary Goldstein
  • Giulio sbrizzai
  • Harut avakian
  • Hrayr Matevosyan
  • Ignazio Scimemi
  • Isabella Garzia
  • J Osvaldo Gonzalez Hernandez
  • Jan Matousek
  • Krzysztof Kurek
  • Leonard Gamberg
  • Marco Contalbrigo
  • Marco mirazita
  • Marco Radici
  • Mariaelena Boglione
  • Markus Diefenthaler
  • Mauro Anselmino
  • Michael Pesek
  • Patrizia Rossi
  • Philip Ratcliffe
  • Rolf Ent
  • Sergio Scopetta
  • Shuddha Shankar Dasgupta
  • Silvia Pisano
  • Simonetta Liuti
  • Stefano Melis
  • Tianbo Liu
  • Vincenzo Barone
Secretary: Serena Baldini
    • 08:45 09:15
      Welcome Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy

      ICTP and organizers

    • 09:15 12:00
      TMD evolution Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Barbara Pasquini (University of Pavia), Mauro Anselmino (Torino University and INFN)
      • 09:20
        TMD evolution -The next stage in the 3D imaging of the nucleon 15m
        Speaker: Mauro Anselmino (Torino University and INFN)
      • 09:50
        TMD evolution: an overview 30m
        In this talk I will present an overview of TMD evolution and of its recent tests and developments
        Speaker: Ignazio Scimemi (U)
      • 10:25
        Phenomenological implementations of TMD evolution 30m
        abstract ....
        Speaker: Stefano Melis (University of Torino and INFN)
      • 11:35
        Effects of TMD evolution and partonic flavor on e+e- annihilation into hadrons 15m
        abstract ....
        Speaker: Andrea Signori (VU University Amsterdam - Nikhef)
    • 11:00 11:30
      coffee 30m
    • 12:00 15:15
      Higher twist and target fragmentation effects Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Marco Mirazita (Istituto Nazionale Fisica Nucleare (IT)), Vincenzo Barone (University of Piemonte Orientale)
      • 12:00
        Disentangling different effects, from higher twist to target fragmentation 30m
        abstract ...
        Speaker: Harut Avakian
      • 12:45
        The Target Fragmentation Region of SIDIS: A Few Remarks 15m
        Speaker: Vincenzo Barone (University of Piemonte Orientale)
      • 14:45
        Lambda production in the DIS target-fragmentation region 15m
        We briefly discuss motivations and physical assumptions of a recently proposed set of Lambda fracture functions obtained by a combined QCD a fit to a variety of semi-inclusive DIS data. We then specialise to CLAS12 kinematics and present predictions for a number of observables sensitive to the assumptions made in the model and which could be used to further improve and/or constrain it.
        Speaker: Federico Alberto Ceccopieri (Universita & INFN, Milano-Bicocca (IT))
      • 15:00
        Lambda production in the DIS target-fragmentation region: the CLAS12 program 15m
        Speaker: Marco Mirazita (Istituto Nazionale Fisica Nucleare (IT))
    • 13:15 14:30
      lunch 1h 15m
    • 15:15 19:00
      TMDs from unpolarised SIDIS data (pT distributions, azimuthal asymmetries) Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Alessandro Bacchetta (University of Pavia), Patrizia Rossi (Laboratori Nazionali di Frascati (LNF)-Istituto Nazionale Fisic), Silvia Pisano (LNF)
      • 15:15
        TMDs from unpolarised SIDIS data - Experimental Overview 30m
        abstract ....
        Speaker: Rolf Ent (Jefferson Lab)
      • 16:00
        Phenomenology: status and perspectives - POSTPONED 15m
        abstract ...
        Speaker: Alessandro Bacchetta (University of Pavia)
      • 16:30
        Unraveling hadron transverse momentum in SIDIS: Dynamics, present data, future measurements 30m
        The transverse momentum of hadrons observed in the current fragmentation region of SIDIS is generally compounded of several parts: the intrinsic transverse momentum of partons in the target, the effects of QCD radiation, and the broadening due to the fragmentation process. Unraveling the different contributions is a major challenge that needs to be addressed before one can reliably apply QCD factorization formulas and extract information about TMD distributions. Recent pion/kaon multiplicity data from HERMES and COMPASS indicate that non-perturbative dynamics plays an essential role in the measured P_T distributions, particularly at z >~ 0.5. In this talk I briefly summarize (a) what our present knowledge of non-perturbative dynamics suggests regarding the magnitude of the different contributions to hadron transverse momentum; (b) what SIDIS measurements could/should be done to unravel the different contributions; (c) what could be learned from measurements of particle correlations between the current and target fragmentation regions. The talk will be a concise summary and aim to provide input to the discussions. It relates mainly to the topics of Sessions 1 and 2 of the program.
        Speaker: Christian Weiss (Jefferson Lab)
      • 17:30
        Multiplicities, azimuthal asymmetries, ... 15m
        see presentation on Thursday morning
        Speaker: Mariaelena Boglione (University of Turin)
      • 18:30
        pT multiplicities at COMPASS 15m
        Speaker: Giulio Sbrizzai (Universita e INFN, Trieste (IT))
    • 16:00 16:30
      coffee 30m
    • 19:00 19:20
      summary -- POSTPONED 20m Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
    • 10:00 15:00
      TMDs from azimuthal asymmetries in transversely and longitudinally polarized SIDIS Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Marco Contalbrigo (Dipartimento di Fisica), Mauro Anselmino (Torino University and INFN)
      • 10:00
        Experimental overview: status and perspectives 30m
        abstract ....
        Speaker: Andrea Bressan (Universita e INFN, Trieste (IT))
      • 11:00
        Phenomenology: status and perspectives 30m
        abstract ....
        Speaker: Mariaelena Boglione (University of Turin)
      • 12:00
        Point by point extraction of the transversity distribution 15m
        The transversity distributions have been recently extracted in a point to point analysis using the Collins and di-hadron asymmetries for p and d, and the corresponding e+e- asymmetries. This alternative method to access transversity (and the other TMD PDFs) has some advantages which are proposed for discussion.
        Speaker: Anna Martin (Trieste University and INFN (IT))
      • 12:25
        An update on the extraction of neutron SSAs from 3He data 15m
        The time reversal-odd parton transverse momentum distributions (TMDs) [1] in the neutron will be studied through polarized SIDIS experiments off 3He, where a high-energy pion is detected in coincidence with the scattered electron (see for example [2]). To disentangle the nuclear and the partonic degrees of freedom an accurate theoretical description of the process is needed. In Ref. [3] the plane wave impulse approximation (IA) was adopted. It was found that the nuclear effects described in IA can be taken into account in a simple effective way, and a procedure to safely extract the neutron SSAs was proposed. In a recent paper [4] the spectator SIDIS process off 3He was studied, and the final state interaction (FSI) between the hadronizing quark and a recoiling deuteron was taken into account through a distorted spin-dependent spectral function. We are now studying the standard SIDIS process, where the FSI between the observed pion and the remnant is again taken into account through a distorted spin-dependent spectral function [5]. The result, very interesting in particular for the experiments planned at the 12 GeV upgrade of JLab [2], is that in the nuclear SSA the effect of FSI cancels to a large extent and the ususal extraction appears to be safe. An extension of the approach to a relativistic treatment will be addressed [6]. REFERENCES [1] V. Barone, F. Bradamante, a. Martin Prog. Part. Nucl. Phys. 65, 267, 2010. [2] G. Cates et al., E12-09-018, JLAB approved experiment, hallaweb.jlab.org/collab/PAC/PAC38//E12-09-018-SIDIS.pdf [3] S. Scopetta, Phys. Rev. D 75, 054005 (2007). [4] L.P. Kaptari, A. Del Dotto, E. Pace, G. Salme` and S. Scopetta, Phys. Rev. C 89, 035206 (2014). [5] A. Del Dotto, L. Kaptari, E. Pace, G. Salme` and S. Scopetta, in preparation. [6] E. Pace, G. Salme`, S. Scopetta, A. Del Dotto and M. Rinaldi, Few Body Syst. 54, 1079 (2013); A. Del Dotto, L.P. Kaptari, E. Pace, G., Sergio Scopetta, Few-Body Syst. 55, 877 (2014).
        Speaker: Sergio Scopetta (Perugia University)
      • 12:55
        The pretzelosity of the nucleon 15m
        Speaker: Bo-Qiang Ma (Peking University)
      • 13:20
        Transversity from GPDs 15m
        Speaker: Gary Goldstein (Tufts University)
      • 13:45
        Collins asymmetries in p p → jet pion X 15m
        We study the azimuthal asymmetries for the distributions of leading pions inside a jet produced inclusively in high-energy proton-proton collisions within the framework of the transverse momentum dependent generalized parton model. We present results for the Collins effect at the RHIC center-of-mass energies $\sqrt{s}$ = 200 and 500 GeV and compare our predictions with very recent, preliminary data from the STAR Collaboration.
        Speaker: Cristian Pisano (Vrije Universiteit Amsterdam)
    • 10:30 11:00
      coffee 30m
    • 13:00 13:30
      lunch 30m
    • 15:00 19:30
      TMD fragmentation functions in e+e- and SIDIS processes Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Andrea Bressan (Universita e INFN, Trieste (IT)), Franco Bradamante (Universita e INFN, Trieste (IT)), Marco Radici (INFN)
      • 15:00
        Phenomenology: status and perspectives 30m
        abstract ....
        Speaker: Marco Radici (INFN)
      • 15:40
        Asymmetry measurements in e+e-: methods, open points and perspectives 30m
        some points which I think wold be valuable to discuss -The correct frame to extract azimuthal correlations in e+e-: The theory is mostly worked out for back-to-back hadrons. However, for experimental and theoretical reasons, two other methods are used: The 'thrust' method and lately modulations in jets. What are the consequences for fits? E.g. are evolution effects different for jets? Will it be possible to use measurements with two soft scales (as thrust or jet method) in global fits? -Extraction of the multidimensional dependence of fragmentation functions: I saw that you plan to have an extensive discussion at of this point. From the e+e- POV the question is probably which kinematic region is in particular important for SIDIS, p+p. There is also a specific IFF question about the importance to extract the different partial wave contributions separately. -Can we formulate observables that are sensitive to Twist3 fragmentation functions in e+e-? I am thinking here about the recently proposed framework by Kanazawa, Koike, Metz and Pitonyak and the twist3 FF that doesn't have a counterpart in the TMD framework. I think it might be difficult to observe in e+e- but maybe worth a discussion. -We use double ratios to cancel acceptance effects and effects from radiative gluons. The effects from radiative gluons are small in simulation. How useful are complicated double ratios in global analysis, e.g. for pi0 we use (pi0pi++pi0pi-)/(pi+p++pi-pi-)
        Speaker: Anselm Vossen
      • 16:30
        Collins asymmetries in e+e- annihilation 15m
        Inclusive hadron production cross section and angular distributions in $e^+e^-$ collisions shed light on fundamental questions of hadronization and fragmentation processes. We present measurements of the so called Collins azimuthal asymmetries in inclusive production of hadron pairs in $e^+e^- \rightarrow h_1h_2X$ annihilation process, where the two hadrons are produced in opposite hemispheres. In particular, we show BaBar preliminary results for $KK$, and $K\pi$ hadron pair combinations, as well as the Collins asymmetries for pion pairs. We also report the preliminary results from the BESIII experiment, which studies pion pairs azimuthal asymmetries using a data set collected at the center-of-mass energy $\sqrt{s}=3.65$ GeV. The comparison between asymmetries measured at B factories ($\sqrt{s}~10.6$ GeV) and those measured at BESIII can be used as a tool to understand the evolution of the Collins fragmentation function.
        Speaker: Isabella Garzia (INFN)
      • 17:05
        Interplay between the Collins and the di-hadron asymmetries 15m
        The recent COMPASS results on the interplay between the Collins asymmetry and the di-hadron asymmetry are briefly presented. Their possible implications on the transversity extraction are discussed. The feasibility of the same studies in e+e- annihilation should also be addressed during the round tables.
        Speaker: Franco Bradamante (Universita e INFN, Trieste (IT))
      • 17:40
        Dependence of 2h SIDIS structure functions on DeltaPhi 15m
        The general formalism to study the dependence of 2h SIDIS structure functions on DeltaPhi. Examples: 1) Sivers effect in 2h production in CFR. a) General formula and convolution expressions for SFs b) Results based on mLEPTO and comparison with released COMPASS data 2) A_LU^sin(DeltaPhi) asymmetry in b2b SIDIS (one hadron produced in the CFR and the second -- in the TFR). Leading order expression based on fracture and fragmentation functions. Preliminary data from JLab CLASS experiment.
        Speaker: Aram Kotzinian (ANSL (Yerevan Physics Institute) (AM))
      • 18:15
        Transverse Spin Effects in Two Hadron Electroproduction 15m
        The measurement of various angular single spin asymmetries (SSA) in a single hadron production off a transversely polarized target in semi-inclusive deep inelastic scattering (SIDIS) process allows to access both the Sivers and Collins effects describing the correlations of the the transverse spin and transverse momenta in both parton distribution and fragmentation functions. In our recent work we have explored both Sivers and Collins effects in the two-hadron SIDIS process. We showed that non-vanishing Sivers-effect-induced SSAs exist for modulations involving sines of the azimuthal angles of both the total and the relative transverse momenta of the hadron pair with respect to the the azimuthal angle of the nucleon's transverse spin. We have made projections for the sizes of these SSAs for the kinematics of the CLAS12 and EIC experiments. Similarly, in the fragmentation of a transversely polarized quark we used the NJL-jet model to demonstrate that Collins effect generates modulations of the polarized fragmentation function involving the sines of the same azimuthal angles of the hadron pair's transverse momenta, now with respect to the transverse quark spin. Moreover, our results for the Collins effect modulations are consistent with the recent experimental measurements by the COMPASS collaboration. These results help to demonstrate that the experimental measurements in two hadron SIDIS process can provide additional information for precise extractions of Sivers and Collins functions.
        Speaker: Hrayr Matevosyan (University of Adelaide)
    • 16:00 16:30
      coffee 30m
    • 20:00 20:30
      dinner 30m
    • 09:00 12:31
      New data analysis methods (multiD and "4pi" measurements, weighted asymmetries, use of generators ...) Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Alessandro Bacchetta (University of Pavia), Anna Martin (Trieste University and INFN (IT)), Marco Radici (INFN)
      • 09:00
        Bessel and p_T weighted asymmetries 30m
        abstract ...
        Speaker: Leonard Gamberg
      • 09:45
        PDF extraction with neural network 15m
        and extension to TMDs
        Speaker: Simonetta Liuti (University of Virginia)
      • 11:10
        "4pi" and multiD measurements 30m
        abstract ...
        Speaker: Marco Contalbrigo (Dipartimento di Fisica)
      • 12:05
        Adaptation of a generator to TMD analysis 15m
        abstract ...
        Speaker: Andrea Bianconi (Brascia University)
    • 10:30 11:00
      coffee 30m
    • 12:30 13:00
      lunch 30m
    • 14:00 15:31
      New channels: Λ, J/Ψ, high pT pairs … production in SIDIS Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
      Conveners: Andrea Bressan (Universita e INFN, Trieste (IT)), Franco Bradamante (Universita e INFN, Trieste (IT)), Marco Radici (INFN)
      • 14:00
        The Gluon Sivers effect measurement at COMPASS from high-pt hadron pairs. 15m
        The COMPASS collaboration has recently released results of the gluon contribution to the Sivers effect measurement from high-pt hadron pairs both for proton and deuteron targets. The analysis method is based on the assumption that in the high Q2 range three processes contribute to the cross section: Leading Process, QCD Compton and Photon Gluon Fusion. The selection of high-pt hadron pairs enhances the fraction of PGF events in the sample and assures weak kinematic dependence of the asymmetries for each process. A novel approach of event-by-event weighting based on Monte Carlo simulations and with the use of Neural Networks is applied to extract all three asymmetries from the same data sample.
        Speaker: Adam Szabelski (National Centre for Nuclear Research (PL))
      • 14:25
        Estimating the gluon Sivers function from A_N data in polarized pp collisions at RHIC 15m
        Within a generalized TMD parton model we use the latest highly precise mid-rapidity data on A_N for inclusive neutral pion production in polarized pp collisions by the PHENIX Collaboration to get a first estimate of the still poorly known gluon Sivers distribution. To this end we adopt present information on the quark Sivers functions as extracted from SIDIS data. These results, together with the recent preliminary analysis on the extraction of gluon Sivers asymmetry in SIDIS by the COMPASS Collaboration can help in clarifying the role of the gluon contribution to the Sivers effect.
        Speaker: Francesco Murgia (INFN - Sezione di Cagliari)
      • 14:50
        Sivers asymmetry of the J/ in COMPASS 2010 proton data 15m
        Speaker: Jan Matousek (Charles University (CZ))
    • 15:30 16:00
      coffee 30m Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy
    • 16:00 18:00
      summary of the Workshop and preparation of the written report 2h Giambiagi Lecture Hall

      Giambiagi Lecture Hall

      Trieste

      Adriatico guesthouse, lower level 1 ICTP - Strada Costiera, 11 I - 34151 Trieste Italy