155 research outputs found
Gluon TMD studies at EIC
A high-energy Electron-Ion Collider (EIC) would offer a most promising tool
to study in detail the transverse momentum distributions of gluons inside
hadrons. This applies to unpolarized as well as linearly polarized gluons
inside unpolarized protons, and to left-right asymmetric distributions of
gluons inside transversely polarized protons, the so-called gluon Sivers
effect. The inherent process dependence of these distributions can be studied
by comparing to similar, but often complementary observables at LHC.Comment: 6 pages, no figures, contribution to the proceedings of the 6th
International conference on Physics Opportunities at an ElecTron-Ion Collider
(POETIC VI), \'Ecole Polytechnique, Palaiseau, France, September 7-11, 201
Gluon TMDs in quarkonium production
Quarkonium production offers good possibilities to study gluon TMDs. In this
proceedings contribution this topic is explored for the linearly polarized
gluons inside unpolarized hadrons and unpolarized gluons inside transversely
polarized hadrons. It is argued that and production at
LHC are best to study the effects of linearly polarized gluons in hadronic
collisions, by means of angular independent ratios of ratios of cross sections.
This can be directly compared to asymmetries in heavy quark pair
and dijet production in DIS at a future high-energy Electron-Ion Collider
(EIC), which probe the same TMDs. In the small- limit this corresponds to
the Weizs\"acker-Williams (WW) gluon distributions, which should show a change
in behavior for transverse momenta around the saturation scale. Together with
investigations of the dipole (DP) gluon distributions, this can provide
valuable information about the polarization of the Color Glass Condensate if
sufficiently small are reached. Quarkonia can also be useful in the study
of single transverse spin asymmetries. For transversely polarized hadrons the
gluon distribution can be asymmetric, which is referred to as the Sivers
effect. It leads to single spin asymmetries in for instance (pair)
production at AFTER@LHC, which probe the WW or -type gluon Sivers TMD. It
allows for a test of a sign-change relation w.r.t. the gluon Sivers TMD probed
at an EIC in open heavy quark pair production. Single spin asymmetries in
backward inclusive -odd quarkonium production, such as production,
may offer probes of the DP or -type gluon Sivers TMD at small -values in
the polarized proton, which in that limit corresponds to a correlator of a
single Wilson loop, describing the spin-dependent odderon.Comment: 9 pages, no figures, contribution to the proceedings of the ECT*
Workshop: New Observables in Quarkonium Production (Quarkonium2016), Trento,
Italy, 28 February - 4 March 201
Overview of Spin Physics at EIC
The possibilities to measure spin effects at a high-energy Electron-Ion
Collider (EIC) are reviewed from a theory point of view. Various types of spin
distributions and promising observables are discussed.Comment: 9 pages; based on an invited talk at the 23rd International Spin
Physics Symposium (SPIN2018), 10-14 September, 2018, Ferrara, Ital
Fine-tuning and the doublet-triplet splitting problem in the minimal GUT
In this paper we analyse the doublet-triplet splitting problem in the minimal
non-super-symmetric GUT. We take into account the full symmetry
breaking pattern with both high scale breaking and electroweak symmetry
breaking. Our analysis shows that the only phenomenologically acceptable model
has three vevs, with a strong hierarchy determined by the minimization
conditions. The amount of fine-tuning in the model is then numerically
evaluated by looking at the effect of variation of input parameters on both the
minimization conditions and the bosonic masses. Regarding the vevs as output
parameters, a large amount of fine-tuning is required in this scenario, which
is an expression of the doublet-triplet splitting problem. We show that this
problem is more general, since a model with coupled scalar sectors will in
general never realise a hierarchy in vevs. To avoid these problems we advocate
imposing the desired hierarchy in vevs as part of the theory. We argue for this
viewpoint because the breaking and electroweak symmetry breaking need
to be adjusted to each other anyway and cannot be regarded as independent
mechanisms. We suggest that not only the symmetry breaking pattern needs to be
imposed, but also the scales at which the breakings happen. We show
quantitatively that the generic theory with hierarchy imposed does not require
any fine-tuning of the free parameters which can all be natural and
perturbative as desired.Comment: 14 pages, 3 figure
Opportunities for spin physics at EIC
This is a brief overview of the spin physics opportunities at a high energy,
high luminosity, polarized Electron-Ion Collider (EIC). It covers measurements
of electroweak polarized structure functions, quark and gluon PDFs, TMDs, GPDs
and GTMDs. Exploiting the many possible final states allows to probe various
spin effects. Open and bound heavy quark production can be used to probe gluon
TMDs, but also color-octet NRQCD long distance matrix elements. Spin-dependent
fragmentation functions can be used too, but are also interesting in
themselves. Especially for studies of the small- and the high- spin
structure the EIC will be essential.Comment: 6 pages, contribution to the Proceedings of the XXVII International
Workshop on Deep-Inelastic Scattering and Related Subjects - DIS2019, 8-12
April, 2019, Torino, Ital
Transient Behaviour in Highly Dependable Markovian Systems: New Regimes, Multiple Paths
In recent years, probabilistic analysis of highly dependable Markovian systems has received considerable attention. Such systems typically consist of several component types, subject to failures, with spare components for replacement while repair is taking place. System failure occurs when all (spare) components of one or several types have failed. In this work we try to estimate the probability of system failure before some fixed time bound via stochastic simulation. Obviously, in a highly dependable system, system failure is a rare event, so we apply importance sampling (IS) techniques, based on knowledge of the behaviour of the system and the way the rare event occurs. In our talk we discern several interesting ways in which the rare event can occur, each of which has its own way of affecting the efficiency of an importance sampling technique
Theoretical aspects of transversity observables
Theoretical aspects of transversity observables are reviewed. The main focus
is on two leading twist transversity single spin asymmetries, one arising from
the Collins effect and one from the interference fragmentation functions.
Electron-positron annihilation experiments which are required to obtain these
fragmentation functions are discussed, as well as the issues of factorization,
evolution and Sudakov factors for the relevant observables. These theoretical
considerations pinpoint the most realistic scenarios towards measurements of
transversity.Comment: 4 pages, uses espcrc2.sty, Talk presented at the "International
Workshop on the Spin Structure of the Proton and Polarized Collider Physics",
ECT*, Trento, Italy, July 23-28, 200
GTMD model predictions for exclusive coherent diffractive production
We extend a previous GTMD model to improve the description of the HERA data
on diffractive dijet production, and include exclusive coherent diffractive
production data. We find that within our gluon GTMD model context and
assumptions, there is considerable tension between the data for these two types
of processes concerning the dependence. Photo- and electroproduction data
for protons and nuclei from EIC and UPC data from LHC and RHIC can help to
establish whether a common GTMD description is possible, as one would expect,
and to facilitate studies of such data we provide predictions for the various
experiments. We point out explicitly in which sense this goes beyond the
description in terms of GPDs.Comment: 15 pages, 19 figures; new references added and some modifications of
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