Searcharxiv⌕ Search

arXiv subjects

Gunnar Ingelman

Publications and source records attributed to Gunnar Ingelman.

30 records · Page 2Linked to original sources
arXiv2007

Heavy Quark Energy Loss Through Soft QCD Scattering in the QGP

A strong suppression of non-photonic electrons in Au+Au collisions is observed at RHIC. This is in disagreement with the expected dominance of the energy loss via gluon radiation, which predicts a much weaker suppression of heavy flavours due to the dead cone effect. However, collisional energy loss is also important, as demonstrated recently by the Soft Colour Interaction Jet Quenching model. Based on this model we show that collisional energy loss of charm quarks gives a suppression of electrons of the observed magnitude, but the contribution from beauty decays, which dominates at intermediate and large pT, results in a somewhat weaker overall suppression of electrons than observed.

hep-ph↗
arXiv2006

Jet Quenching from soft QCD Scattering in the Quark-Gluon Plasma

We show that partons traversing a quark-gluon plasma can lose substantial amounts of energy also by scatterings, and not only through medium-induced radiation as mainly considered previously. Results from Monte Carlo simulations of soft interactions of partons, emerging from a hard scattering, through multiple elastic scatterings on gluons in an expanding relativistic plasma show a sizeable jet quenching which can account for a substantial part of the effect observed in RHIC data.

hep-ph↗
arXiv2005

Hard diffraction -- 20 years later

The idea of diffractive processes with a hard scale involved, to resolve the underlying parton dynamics, was published 1985 and experimentally verified 1988. Today hard diffraction is an active research field with high-quality data and new theoretical models. The trend from Regge-based pomeron models to QCD-based parton level models has given insights on QCD dynamics involving perturbative gluon exchange mechanisms, including the predicted BFKL-dynamics, as well as novel ideas on non-perturbative colour fields and their interactions. Extrapolations to the LHC include the interesting possibility of diffractive Higgs production.

hep-ph↗
arXiv2005

Hard Diffraction -- from Blois 1985 to 2005

The idea of diffractive processes with a hard scale involved, to resolve the underlying parton dynamics, was presented at the first Blois conference in 1985 and experimentally verified a few years later. Today hard diffraction is an active research field with high-quality data and new theoretical models. The trend from Regge-based pomeron models to QCD-based parton level models has given insights on QCD dynamics involving perturbative gluon exchange mechanisms, including the predicted BFKL-dynamics, as well as novel ideas on non-perturbative colour fields and their interactions.

hep-ph↗
arXiv2005

Lunar Satellite Detection of Ultra-High Energy Neutrinos with the Use of Radio Methods

Neutrinos interact with matter only through weak processes with low cross-section. To detect cosmic neutrinos most efforts have relied on the detection of visible Vavilov-Cerenkov light in detectors embedded in the target volumes. To access the decreasing flux of ultra-high energy neutrinos, far above 1 PeV, ideas on how to increase the detection volume by observing coherent radio frequency emission caused by the Askaryan effect have been put forward. Here we describe how a satellite in lunar orbit equipped with an electromagnetic vector sensor could detect Askaryan pulses induced by neutrinos interacting with the moon. The threshold neutrino energy is found to be 50 EeV for this setup, and the sensitivity is determined from simulations. A model dependent event rate of 2.2 events per year is calculated.

astro-ph↗
arXiv2005

Quark asymmetries in the proton from a model for parton densities

Based on quantum fluctuations in momentum and of the proton into meson-baryon pairs, we develop a physical model for the non-perturbative x-shape of parton density functions in the proton. The model describes the proton structure function and gives a natural explanation of observed quark asymmetries, such as the difference between the anti-up and anti-down sea quark distributions and between the up and down valence distributions. An asymmetry in the momentum distribution of strange and anti-strange quarks in the nucleon is found to reduce the NuTeV anomaly to a level which does not give a significant indication of physics beyond the standard model.

hep-ph↗
arXiv2004

Strange quark asymmetry in the nucleon and the NuTeV anomaly

The NuTeV anomaly of a non-universal value of the fundamental parameter sin^2θ_W in the electroweak theory has been interpreted as an indication for new physics beyond the Standard Model. However, the observed quantity depends on a possible asymmetry in the momentum distributions of strange quarks and antiquarks in the nucleon. This asymmetry occurs naturally in a phenomenologically successful physical model for such parton distributions, which reduces the NuTeV result to only about two standard deviations from the Standard Model.

hep-ph↗
arXiv2004

Interpretation of electron-proton scattering at low Q^2

Low-Q^2 photons do not resolve partons in the proton, which gives problems when applying the deep inelastic scattering formalism, such as an unphysical, negative gluon density extracted from data. Considering instead hadronic fluctuations of the photon, we show that the generalised vector meson dominance model (GVDM) gives a good description of the measured cross section at low Q^2, i.e. reproduces F_2(x,Q^2), using only few parameters with essentially known values. Combining GVDM and parton density functions makes it possible to obtain a good description of F_2 data over the whole range of x and Q^2.

hep-ph↗
arXiv2003

Generalized VDM and F_2 data at low Q^2

The generalised vector meson dominance model (GVDM) gives a good description of F_2 data at very low Q^2. At intermediate Q^2 a GVDM component avoids problems when applying the large-Q^2 DIS formalism, such as a negative gluon distribution in the proton. The fluctuations of the exchanged photon into vector mesons is also a natural part of a model with hadronic fluctuations of the target proton, which gives a good description of the non-perturbative x-shape of the proton's parton density functions at the starting scale Q^2_0 for DGLAP evolution.

hep-ph↗
arXiv2002

String model description of polarisation and angular distributions in pbar p -> Lambdabar Lambda at low energies

The observed polarisation of Lambda hyperons from the inclusive pA -> Lambda X reaction at high energies has previously been well described within the Lund string model through polarised ss quark pair production in the string breaking hadronisation process. This model is here applied to the exclusive pbar p -> Lambdabar Lambda reaction at low energies and compared to available data sets down to an incident beam momentum of 1.835 GeV/c. This required an extension of the diquark scattering model to involve three components: an isotropic part relevant close to threshold, a spectator part and a forward scattering part as in pA -> Lambda X at high energies. The observed angular distributions are then reproduced and, for momentum transfers above |t'| = 0.2 GeV^2, agreement with the measured polarisation is also obtained.

hep-ph↗
arXiv1999

Diffractive Hard Scattering

Diffraction is an old subject which has received much interest in recent years due to the advent of diffractive hard scattering. We discuss some theoretical models and experimental results that have shown new striking effects, e.g. rapidity gaps in jet and W production and in deep inelastic scattering. Many aspects can be described through the exchange of a pomeron with a parton content, but the pomeron concept is nevertheless problematic. New ideas, e.g. based on soft colour interactions, have been introduced to resolve these problems and provide a unified description of diffractive and non-diffractive events. This is part of the general unsolved problem of non-perturbative QCD and confinement.

hep-ph↗