arXiv subjects

Halina Abramowicz

Publications and source records attributed to Halina Abramowicz.

15 recordsLinked to original sources

arXiv2021

Conceptual Design Report for the LUXE Experiment

This Conceptual Design Report describes LUXE (Laser Und XFEL Experiment), an experimental campaign that aims to combine the high-quality and high-energy electron beam of the European XFEL with a powerful laser to explore the uncharted terrain of quantum electrodynamics characterised by both high energy and high intensity. We will reach this hitherto inaccessible regime of quantum physics by analysing high-energy electron-photon and photon-photon interactions in the extreme environment provided by an intense laser focus. The physics background and its relevance are presented in the science case which in turn leads to, and justifies, the ensuing plan for all aspects of the experiment: Our choice of experimental parameters allows (i) effective field strengths to be probed at and beyond the Schwinger limit and (ii) a precision to be achieved that permits a detailed comparison of the measured data with calculations. In addition, the high photon flux predicted will enable a sensitive search for new physics beyond the Standard Model. The initial phase of the experiment will employ an existing 40 TW laser, whereas the second phase will utilise an upgraded laser power of 350 TW. All expectations regarding the performance of the experimental set-up as well as the expected physics results are based on detailed numerical simulations throughout.

hep-ex↗

arXiv2016

Particle physics perspective

A personal perspective on the future challenges of research in particle physics is presented with emphasis on the role of DIS physics in this endeavour.

hep-ex↗

arXiv2013

Physics at the CLIC e+e- Linear Collider -- Input to the Snowmass process 2013

This paper summarizes the physics potential of the CLIC high-energy e+e- linear collider. It provides input to the Snowmass 2013 process for the energy-frontier working groups on The Higgs Boson (HE1), Precision Study of Electroweak Interactions (HE2), Fully Understanding the Top Quark (HE3), as well as The Path Beyond the Standard Model -- New Particles, Forces, and Dimensions (HE4). It is accompanied by a paper describing the CLIC accelerator study, submitted to the Frontier Capabilities group of the Snowmass process.

hep-ex↗

arXiv2010

Forward Instrumentation for ILC Detectors

Two special calorimeters are foreseen for the instrumentation of the very forward region of the ILC detector, a luminometer designed to measure the rate of low angle Bhabha scattering events with a precision better than 10-3 and a low polar angle calorimeter, adjacent to the beam-pipe. The latter will be hit by a large amount of beamstrahlung remnants. The amount and shape of these depositions will allow a fast luminosity estimate and the determination of beam parameters. The sensors of this calorimeter must be radiation hard. Both devices will improve the hermeticity of the detector in the search for new particles. Finely segmented and very compact calorimeters will match the requirements. Due to the high occupancy fast front-end electronics is needed. The design of the calorimeters developed and optimised with Monte Carlo simulations is presented. Sensors and readout electronics ASICs have been designed and prototypes are available. Results on the performance of these major components are summarised.

physics.ins-det↗

arXiv2009

The HERA challenges for LHC

Over the last two decades, the HERA collider has provided a large amount of new information about QCD dynamics at high energy. While the most appreciated are the measurements of the proton structure functions in a wide range of parton momentum x and virtuality Q^2, it is hard to believe that some of the observations at HERA which do not fit the simple picture of DGLAP dynamics would not get amplified at the LHC, possibly rendering certain approaches to searches beyond the Standard Model inadequate.

hep-ex↗

arXiv2005

The Pomeron structure and diffractive parton distributions

Measurements of the diffractive structure function, $F_2^D$, of the proton at HERA are used to extract the partonic structure of the Pomeron. Regge Factorization is tested and is found to describe well the existing data within the selected kinematic range. The analysis is based on the next to leading order QCD evolution equations. The results obtained from various data sets are compared. An analysis of the uncertainties in determining the parton distributions is provided. The probability of diffraction is calculated using the obtained results.

hep-ph↗

arXiv2005

NLO photon parton parametrization

An NLO photon parton parametrization is presented based on the existing $F_2^γ$ measurements from $e^+e^-$ data and the low-$x$ proton structure function from $ep$ interactions. Also included in the extraction of the NLO parton distribution functions are the dijets data coming from $γp \to j_1 + j_2 +X$. The new parametrization is compared to other available NLO parametrizations.

hep-ph↗

arXiv2004

Diffractive Scattering

Recent experimental results on inclusive diffractive scattering and on exclusive vector meson production are reviewed. The dynamical picture of hard diffraction emerging in perturbative QCD is highlighted.

hep-ex↗

arXiv2004

The ALLM parameterization of sigma_{tot}(gamma* p) - an update

The ALLM parameterization of sigma_{tot}(gamma* p) has been updated by using all published F_2 data to determine its parameters. The fit yields a chi^2/ndf of 0.97 for the 1356 data points. The updated ALLM parameterization, ALLM97, gives a good description of all the available data in the whole x and Q^2 range studied so far (3\times10^{-6} < x < 0.85, 0 \le Q^2 < 5000 GeV^2).

hep-ph↗

arXiv2000

Diffraction and the Pomeron

hep-ph↗

arXiv1999

HERA Collider Physics

HERA, the first electron-proton collider, has been delivering luminosity since 1992. It is the natural extension of an impressive series of fixed-target lepton-nucleon scattering experiments. The increase of a factor ten in center-of-mass energy over that available for fixed-target experiments has allowed the discovery of several important results, such as the large number of slow partons in the proton, and the sizeable diffractive cross section at large $Q^2$. Recent data point to a possible deviation from Standard Model expectations at very high $Q^2$, highlighting the physics potential of HERA for new effects. The HERA program is currently in a transition period. The first six years of data taking have primarily elucidated the structure of the proton, allowed detailed QCD studies and had a strong impact on the understanding of QCD dynamics. The coming years will bring the era of electroweak studies and high $Q^2$ measurements. This is therefore an appropriate juncture at which to review HERA results.

hep-ex↗

arXiv1996

Tests of QCD at low $x$

This talk reviews the latest measurements of the proton, Pomeron and photon structure functions. These measurements, especially at low $x$ and/or low $Q^2$ lead to new insight into the picture of hadronic interactions.

hep-ex↗

arXiv1996

An Orientation Selective Neural Network and its Application to Cosmic Muon Identification

We propose a novel method for identification of a linear pattern of pixels on a two-dimensional grid. Following principles employed by the visual cortex, we employ orientation selective neurons in a neural network which performs this task. The method is then applied to a sample of data collected with the ZEUS detector at HERA in order to identify cosmic muons which leave a linear pattern of signals in the segmented uranium-scintillator calorimeter. A two dimensional representation of the relevant part of the detector is used. The results compared with a visual scan point to a very satisfactory cosmic muon identification. The algorithm performs well in the presence of noise and pixels with limited efficiency. Given its architecture, this system becomes a good candidate for fast pattern recognition in parallel processing devices.

hep-ex↗

arXiv1995

Production of large rapidity gap events in ep interactions at HERA

This is a short review of the properties of electron proton interactions characterized by the presence of large rapidity gaps (LRG) in the measured hadronic final state as obtained by the ZEUS Collaboration at the HERA Collider. In the deep inelastic neutral current $ep$ interactions, the factorization properties of the LRG events interpreted as due to the diffractive dissociation of the virtual photon are compatible with expectations from the Regge phenomenology of soft interactions. The measurement of deep inelastic scattering combined with results from photoproduction of high $p_T$ jets are successfully interpreted in terms of a factorizable Pomeron consisting of quarks and with a substantial contribution of a gluonic component. The first hints of a more complicated nature of the Pomeron are observed in the deep inelastic exclusive $ρ^o$ production, where a strong increase of the production cross section with energy is observed relative to the measurements of the NMC Collaboration at lower energy.

hep-ex↗

arXiv1995

Interplay of Hard and Soft Physics in Small $x$ Deep Inelastic Processes

Coherence phenomena, the increase with energy of coherence length and the non-universality of parton structure of the effective Pomeron are explained. New hard phenomena directly calculable in QCD such as diffractive electroproduction of states with $M^2\ll Q^2$ and the color transparency phenomenon as well as new options to measure the light-cone wave functions of various hadrons are considered. An analogue of Bjorken scaling is predicted for the diffractive electroproduction of $ρ$ mesons at large momentum transfers and for the production of large rapidity gap events, as observed at HERA. A phenomenological QCD evolution equation is suggested to calculate the basic characteristics of the large rapidity gap events. The increase of parton densities at small $x$ as well as new means to disentangle experimentally soft and hard physics are considered. We discuss constraints on the increase of deep inelastic amplitudes with $Q^2$ derived from the inconsistency of QCD predictions for inclusive and exclusive processes and from unitarity of the S matrix for collisions of wave packets. New ways to probe QCD physics of hard processes at large longitudinal distances and to answer the long standing problems on the origin of the Pomeron are suggested. Unresolved problems and perspectives of small $x$ physics are also outlined.

hep-ph↗