Conveners
Afternoon: Session 3
- Alessandro Bacchetta (University of Pavia)
Afternoon: Session 4
- Gunar Schnell
Afternoon: Session 3
- Fulvio Tessarotto (Universita e INFN Trieste (IT))
Afternoon: Session 3
- Jan Friedrich (Technische Universitaet Muenchen (DE))
Afternoon: Session 4
- Harut Avakian
The HERMES experiment collected from 1995 to 2007 a wealth of deep-inelastic scattering data using 27.6 GeV longitudinally polarised electrons and positrons and various unpolarised as well as longitudinally and transversely polarised gas targets. This allowed for a series of diverse measurements. Among them are measurements in semi-inclusive deep-inelastic scattering that provide information...
In 2016 and 2017 the COMPASS Collaboration at CERN collected a large sample of DIS events with a longitudinally polarized 160 GeV/$c$ muon beam scattering off a liquid hydrogen target. A small subsample of the collected data has been analysed to extract preliminary results for the transverse momentum dependent charged hadron multiplicities and the amplitudes of the azimuthal modulations...
We present preliminary COMPASS results on pion and kaon multiplicities produced in semi-inclusive deep inelastic scattering of 160 GeV muons off a pure proton (LH2) target. The results constitute a data set of more than 600 points for pions and 600 for kaons, covering a large x, Q2 and z domain in a fine binning with W>5 GeV2. The results from the sum of the z-integrated multiplicities M(π+) +...
Considering polarization degrees of freedom in the final state of hard, semi-inclusive interactions allows a more focused access to the partonic structure of the nucleon. The respective fragmentation functions can be used to study QCD in the non-perturbative regime complementary to polarized (TMD) PDFs.
This talk will discuss recent and anticipated results on polarized fragmentation functions...
Recent BELLE measurements provide the cross section for single hadron production in e+e- annihilations, differential in the hadron transverse momentum with respect to the thrust axis. Universality breaking effects due to process-dependent soft factors make it very difficult to relate this cross section to that corresponding to hadron-pair production in e+e- annihilations, where TMD...
The mysterious asymmetry of the anti-quarks inside nucleon remains to be investigated. The experiment SeaQuest, with unpolarized targets, aims to do so. The experiment finished data collection in 2017. A preliminary result will be given in this presentation. The spin structure of the nucleon remains a mystery. Recent studies suggest that the orbital angular momentum of sea quarks could...
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 (in)dependent azimuthal asymmetries arising in the Drell-Yan cross-section.
In 2015 and 2018, COMPASS...
Power-supressed O(qT^2/Q^2) corrections to the Drell-Yan TMD cross-sections and structure functions, which restore QED gauge-invariance of the hadronic tensor in TMD factorization will be discussed in a framework of Parton Reggeization Approach [1,2]. These corrections are important in the region of moderate qT~Q for the description of qT-spectrum and Helicity Structure Functions, and are not...
AMBER is a newly proposed experiment at CERN with the aim of contributing in the field of QCD. Among several ideas, the measurement of the pion induced Drell-Yan with the two pion charges is one of the proposed measurements. The combination of the two pion charges together with a carbon target gives access to observables sensitive to the separation between sea and valence in the pion. In...
Parton Reggeization approach (PRA) is based on $k_T$-factorization of hard processes at multi-Regge kinematics. In PRA, initial state partons are treated as Reggeized gluons and Reggeized quarks, which are quantum fields of Lipatov's Effective Theory [1]. This one guarantees gauge invariance for off-shell hard amplitudes. As it was shown in [2], unintegrated (transverse momentum dependent)...
Prompt photon production in hadronic collisions is a proven way to access unpolarised and polarised gluon structure of hadrons. Possible physics with prompt photons at the COMPASS-AMBER experiment at CERN and at the SPD experiment at the NICA collider at JINR (Dubna, Russia) will be presented.
The transverse single spin asymmetry of a nucleon is discussed for the semi-inclusive production of photons in lepton-nucleon collisions. Arguments are given that this particular observable is very suitable to study quark-gluon correlation functions in the nucleon. Experimental data, for example taken at a future Electron-Ion Collider, on this observable may help to constrain these correlation...
Light vector mesons $V=\rho,\omega,\varphi, K^*$ etc. can be transversely (helicity $\lambda=\pm 1$) or longitudinally ($\lambda=0$ ) polarized.\
Has their polarization impact on their interaction with nucleons and nuclei?\
The unstable meson total cross section with nucleon can be extracted by measuring the absorption of mesons in the production off nuclei as
the nuclear absorption...
We report an observation of new properties of valence quark partonic
distribution that allows to derive new relations that can be used to constrain
phenomenological parameterizations of PDFs. These relations allow
to formulate a “mean field theorem” according to which no fixed number
constituent exchanges can be responsible for the valence quark distributions
in 0.1 < x < 0.3 region. ...
For a complete description of the strong interaction, Quantum Chromodynamics (QCD) must be able to predict the dynamics of the free quarks in the nuclear medium. Put another way, the nucleus is a good laboratory to study the propagation of free quarks and the formation of color-neutral objects. This talk will describe a program at Hall B at the Thomas Jefferson National Accelerator Facility...
Baryon-to-meson Transition Distribution Amplitudes (TDAs) appear
as building blocks within the collinear factorized description of amplitudes
for a class of hard exclusive reactions such as hard exclusive meson
electroproduction off a baryon in the near-backward region and
baryon-antibaryon annihilation into a meson and a lepton pair.
In this talk we present a general overview of the...
Atomic nuclei are made of protons and neutrons, themselves composed of quarks and gluons. Understanding how the nuclear environment impacts the quark-gluon structure of bound nucleons is an outstanding challenge. While the first evidence for such impact, known as the ‘EMC effect’, was observed over 35 years ago, a generally accepted explanation of the dynamics driving it is still lacking. I...
A discussion of Stan Brodsky's work shortly before and after the discovery of the J/psi particle.
