Conveners
QCD, spin physics and chiral dynamics
- Salvatore Fazio
- Catarina Quintans (LIP)
- Miguel Echevarria (University of Alcalá)
QCD, spin physics and chiral dynamics
- Catarina Quintans (LIP)
- Salvatore Fazio
- Miguel Echevarria (University of Alcalá)
Description
Information for speakers about talk's duration:
18 min slot= 15 to speak + 3 for questions
15 min slot= 12 to speak + 3 for questions
We present a new release of the NNPDF family of global analyses of parton distribution functions: NNPDF4.0. It includes a wealth of new experimental data from HERA and the LHC, from dijet cross-sections to single-top and top-quark pair differential distributions. The NNPDF4.0 methodology benefits from improved machine learning algorithms, in particular automated hyperparameter optimisation and...
Deeply Virtual Compton Scattering (DVCS) and Hard Exclusive Meson Production (HEMP) are very promising reactions to study Generalized Parton Distributions (GPDs). GPDs correlate the longitudinal momentum of the partons to their transverse spatial distribution inside the nucleon, and thus provide the 3-dimensional structure of the nucleon in QCD. Following a one-month test run in 2012,...
The COMPASS experiment, located in the North Area of CERN, has the study of nucleon structure as one of its main physics goals. In 2015 and 2018, COMPASS collected Drell-Yan and J/$\psi$ production data from the collisions of a 190 GeV negative pion beam on a transversely polarized ammonia target, and on a tungsten target. The study of the angular dependence of the dimuons produced provides...
The HERMES experiment has collected a wealth of data using the 27.6 GeV polarized HERA lepton beam and various polarized and unpolarized gaseous targets. This allows for a series of unique measurements of observables sensitive to the multidimensional (spin) structure of the nucleon, in particular semi-inclusive deep-inelastic scattering (SIDIS) measurements, for which the HERMES dual-radiator...
A key step towards a better understanding of nucleon structure in terms of generalized parton distributions (GPDs) is the measurement of deeply virtual Compton scattering off the neutron (nDVCS; $ed\to e'n\gamma(p)$). This process emphasizes mainly, in the kinematic range covered at Jefferson Lab, the access to the GPD E of the neutron which is the least constraind GPD up till now. The...
Generalized Parton Distributions (GPDs) describe the correlations between the longitudinal momentum and the transverse position of the partons inside the nucleon. They are nowadays the subject of an intense effort of research, in the perspective of understanding nucleon spin and mechanical properties.
In this talk, we present the first observation of the Timelike Compton Scattering (TCS)...
Measurements of the proton's form factor ratio made with polarization transfer show a striking discrepancy relative to the ratio extracted from unpolarized elastic electron-proton scattering cross sections. One hypothesis is that the discrepancy is caused by hard two-photon exchange (TPE), a typically neglected radiative correction that may bias the two approaches differently. This hypothesis...
The analysis of single transverse-spin asymmetries (SSAs) gives us tremendous insight into the internal structure of hadrons. For example, the Sivers and Collins effects in semi-inclusive deep-inelastic scattering (SIDIS), Sivers effect in Drell-Yan, and the Collins effect in electron-positron annihilation have been widely investigated over many years in order to perform 3D momentum-space...
We calculate single-logarithmic corrections to the small-$x$ flavor-singlet helicity evolution equations derived recently in the double-logarithmic approximation. The new single-logarithmic part of the evolution kernel sums up powers of $\alpha_s\ln(1/x)$, which are an important correction to the dominant powers of $\alpha_s\ln^2(1/x)$ summed up previously by the double-logarithmic kernel at...
We present the first-ever description the world data on the $g_1^{p,n}$ structure function at small Bjorken $x$ using evolution equations in $x$ derived from first principles QCD. This is a Monte-Carlo analysis within the JAM global framework that allows us to fit all existing polarized DIS data below $x<0.1$ as well as predict future measurements of small $x$ $g_1^{p,n}$ at the EIC. This is a...
We present a new global QCD analysis of unpolarized and polarized data, using a Monte Carlo approach to simultaneously extract both the spin-averaged and helicity PDFs. We focus on the light quark sea asymmetries, including new data from the SeaQuest experiment and $W$-lepton production at RHIC. For the first time we extract a nonzero light quark sea asymmetry for the helicity PDFs through a...
In recent years the measurements of spin and azimuthal asymmetries (SSAs) in final state hadronic distributions in semi-inclusive processes have been widely used to access the underlying Transverse Momentum Dependent (TMD) parton distributions. The detailed understanding of the orbital structure of partonic distributions, encoded in TMD PDFs has been widely recognized as one of the key...
Two-particle azimuthal correlation has been proposed to be one of the most direct and sensitive channels to access the nonlinear gluon dynamics in nuclei. Color Glass Condensate (CGC) predicts a suppression of back-to-back correlation in $p(d)+$A collisions compared to $p$$+$$p$ collisions. In $d+$A collisions, the double-parton scattering (DPS) can be an alternative explanation of the...
The STAR experiment at RHIC has measured transverse single-spin asymmetries of W$^±$/$Z_0$-bosons in proton-proton collisions at a center-of-mass energy $\sqrt{s}$ = 510 GeV (2017 data). These asymmetries probe correlations between parton motion and the proton spin in the initial state which are described in terms of transverse momentum dependent parton distribution functions (TMD), in this...
There have been numerous results in both longitudinal and transverse spin at PHENIX. The longitudinal double spin asymmetry (A_{LL}) provides insight into the gluon helicity distribution function ({Delta}G), the contribution of gluon spin to the proton. The A_{LL} of direct photons, jets, and charged pions in polarized pp collisions at \sqrt{s} = 510 GeV have been measured, which are novel...
Jets encode the full evolution between the partonic state immediately following a hard-scattering interaction and the hadronic state measured in particle detectors. While only approximately 60% of the jet content corresponds to charged particles, this content can be measured with significantly higher precision than neutral particles such as photons or neutral hadrons. These measurements can be...
An important property of the strong interaction that is potentially observable in heavy-ion collisions is local parity violation which manifests itself as a charge separation along the direction of the magnetic field. This phenomenon is called the Chiral Magnetic Effect (CME). A similar effect in which the presence of a vector charge (e.g., electric charge) causes a separation of chiralities...
Recent results from the proton-proton collision data taken by the ATLAS experiment on the charmonium production and on the B_c production and decays will be presented. The measurement of the associated production of the J/psi meson and a gauge boson, including the separation of single and double parton scattering components, will be discussed. The measurement of J/psi and psi(2S) differential...
The Drell-Yan hadronic tensor is calculated in the Sudakov region $s\gg Q^2\gg q_\perp^2$ with ${1\over Q^2}$ accuracy, first at the tree level and then with the double-log accuracy. It is demonstrated that in the leading order in $N_c$ the higher-twist quark-quark-gluon TMDs reduce to leading-twist TMDs due to QCD equation of motion. The resulting tensor for unpolarized hadrons is EM...
We use soft collinear effective theory (SCET) to study a dijet production process in deep-inelastic-scattering (DIS), measuring the imbalance of the two hard probes in the Breit frame. In order to achieve factorization of the transverse momentum dependent (TMD) cross-section, we need to introduce a new soft function that we calculate at one-loop, regulating rapidity divergencies with the...
We perform explorative analyses of the 3D gluon content of the proton via a study of polarized T-odd gluon TMDs at twist-2, calculated in a spectator model for the parent nucleon. Our approach encodes a flexible parameterization for the spectator-mass density, suited to describe both moderate and small-xx effects. All these prospective developments are relevant in the investigation of the...
We present the first-ever QCD analysis of the semi-inclusive DIS $A^{cos(\phi_h-\phi_S)}_{LT}$ data using Monte Carlo techniques to extract the worm-gear TMD $g_{1T}$. The relevant data are available from COMPASS, HERMES and JLab. We compare our results for $g_{1T}$ with different theoretical approaches, including the large-$N_c$ approximation, the Wandzura-Wilczek-type approximation, and lattice QCD.
We study the transverse polarization of hyperons produced
in semi-inclusive deep inelastic scattering, $ep \to e\Lambda^{\uparrow}X$,
in the collinear twist-3 factorization. This process receives three types of
twist-3 contributions: (i) twist-3 distribution in the initial proton combined
with the transversity fragmentation function (FF) for the hyperon,
(ii) Twist-3 quark FFs for the...
Nucleon-nucleon interaction
is studied within chiral effective field theory with a finite cutoff
at next-to-leading order in the chiral expansion.
The leading order interaction is resummed in a non-perturbative manner,
whereas the next-to-leading-order terms are treated perturbatively.
Some aspects of renormalizability of such a scheme are addressed.
In particular, it is analyzed whether...
Charged particle multiplicity distributions in positron-proton deep inelastic scattering at a centre-of-mass energy $\sqrt{s}=319$ GeV are measured. The data are collected with the H1 detector at HERA corresponding to an integrated luminosity of $136$ pb$^{-1}$. Charged particle multiplicities are measured as a function of photon virtuality $Q^2$, inelasticity $y$ and pseudorapidity $\eta$ in...
First measurements of the 1-jettiness event shape observable in the Breit Frame and of jet production in the laboratory frame, close to the Born-level configuration, are performed in neutral-current deep-inelastic scattering at HERA. The data were recorded with the H1 detector in the years 2003-2007 and are restricted to high momentum transfer $Q^2 > 150$ GeV$^2$. The 1-jettiness observable...
The R value, defined as the ratio of the inclusive hadronic cross section and the muon cross section in e+e- collisions, is an important input for the calculation of the Standard Model predictions of the anomalous magnetic moment of the muon a_mu and the running of the QED coupling constant alpha_QED(m_Z) evaluated at Z pole. The BESIII collaboration has collected data with high statistics to...
Nucleons are one of the most fundamental building blocks of ordinary matter, yet their internal structure and dynamics are still not fully understood. Electromagnetic form factors allow to investigate fundamental properties of the nucleon. The BESIII collaboration has studied the time-like form factors of the proton using the energy scan and the ISR technique. The |GE/GM| ratio is obtained...
The Spin Physics Detector at the constructing NICA collider (JINR, Dubna) is a universal facility to investigation the spin structure of the proton and deuteron and the other spin-related phenomena with polarized proton and deuteron beams at a collision energy up to 27 GeV. Comprehensive study of the unpolarized and polarized gluon content of the nucleon at large Bjorken-x using different...
The goal of LHCspin is to develop, in the next few years, innovative solutions and cutting-edge technologies to access spin physics in high-energy polarized fixed-target collisions, by exploring a unique kinematic regime given by the LHC beam and by exploiting new probes.
This ambitious task poses its basis on the recent installation of SMOG2, the unpolarized gas target in front of the LHCb...
The PANDA experiment is a core project of the future Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt. It will measure annihilation reactions induced by a high intensity antiproton beam of momentum in the range between 1.5 GeV/c and 15 GeV/c. An important part of the PANDA physics program will be dedicated to the investigation of the nucleon structure using electromagnetic...
We calculate the spin-averaged generalized parton distributions (GPDs) of sea quarks in the proton at zero skewness from nonlocal covariant chiral effective theory, including one-loop contributions from intermediate states with pseudoscalar mesons and octet and decuplet baryons. A relativistic regulator is generated from the nonlocal Lagrangian where a gauge link is introduced to...
In the light of recent experimental progress in determining the pressure and shear distributions in the proton, these quantities are calculated in a model with confined quarks supplemented by the pion field required by chiral symmetry. The incorporation of the pion contributions is shown to account for the long-range distributions, in general agreement with the experimentally extracted quark...
We make an analysis of the isospin symmetry for fragmentation functions assuming isospin symmetry in strong interactions. Taking hadron decay contributions into account, we show that the isospin symmetry is held for \Lambda hyperon fragmentation functions. Only tiny violations are allowed for other hadrons due to weak decays. We also present a rough estimate for the magnitudes of such...
I’ll discuss the role of the chiral anomaly in deep inelastic scattering (DIS) of electrons off polarized protons employing a worldline formalism, which is a powerful framework for the computation of perturbative multi-leg Feynman amplitudes. I’ll demonstrate how the triangle anomaly appears at high energies in the DIS box diagram for the polarized structure function $g_1(x_B,Q^2)$ in both the...
Hadronic matrix elements of the QCD energy-momentum tensor can be parametrized in terms of gravitational form factors (GFFs) which, through their dependence on momentum transfer and decomposition into quark and glue contributions, encode information about the distributions of energy, angular momentum, pressure, and shear forces within a hadron spatially and amongst its constituents. GFFs can...
