arXiv subjects

Wieslaw Placzek

Publications and source records attributed to Wieslaw Placzek.

13 recordsLinked to original sources

arXiv2026

Deep inelastic scattering as a probe of entanglement: the complete QCD dipole cascade

We study entanglement entropy in Deep Inelastic Scattering (DIS) using the dipole formulation of the high-energy limit of QCD. We argue that a reduced density matrix arises in low $x$ DIS due to a trace over unobserved color degrees of freedom and we obtain entanglement entropy in terms of dipole multiplicities, directly from the von Neumann entropy. Dipole multiplicities are obtained from a solution to low $x$ evolution equations, which we solve numerically. Unlike previous studies, we take into account both transverse-size and azimuthal-angle dependence in the dipole evolution kernel. We study both the exact solution of the equation as well as its double leading-logarithmic approximation (DLLA). We find that for the same initial dipole size, the DLLA solution generates a larger entropy. Finally, we calculate the dipole multiplicities and entanglement entropy and compare our results to the Shannon entropy of hadron multiplicities, as measured by the H1 collaboration.

hep-ph↗

arXiv2025

Predictions for photon-jet correlations at forward rapidities in heavy-ion collisions

In this work, we study for the first time jet-medium interactions in heavy-ion collisions with introduction of saturation and Sudakov effects with parameters tuned for upcoming forward calorimeter acceptances in experiments, in particular the ALICE FoCal detector. We focus on $γ+$jet correlations by taking into account in-medium parton evolution using the BDIM equation that describes jet interactions with the quark-gluon plasma (QGP) combined with vacuum-like emissions (VLE). We systematically introduce the early time gluon saturation dynamics through the small-$x$ Improved Transverse Momentum Dependent factorization (ITMD). For our purpose, we use Monte Carlo programs KATIE and TMDICE to generate hard events and in-medium parton evolution, respectively. We present results of azimuthal correlations and nuclear modification ratios to gauge the impact of the gluon saturation effects at early time for the in-medium jet energy loss.

hep-ph↗

arXiv2024

Efficient transmutation of long-lived fission products in a Gamma Factory beam driven advanced nuclear energy system

The Gamma Factory (GF) project aims to generate high-intensity $γ$-ray beams of tunable energy and relatively small energy spread. Such beams can be optimized to generate an intense photo-neutron source, capable of driving an advanced nuclear energy system (ANES) for nuclear waste transmutation and supplying electrical power that is necessary for the GF operation mode of the Large Hadron Collider storage ring. In this study, we investigate the feasibility of driving ANES with the GF beam which is optimized to maximize the neutron production rate. The dependence of the ANES thermal power on the distance between the positions of the ANES and the GF $γ$-ray source is evaluated. For the $γ$-ray beam reaching the intensity of $\sim$$10^{19}$ photons per second, the ANES thermal power could exceed $500\,$MWt. Under the assumption that ANES operates over $20$ years, the transmutation rate could reach $30\%$ for five typical long-lived fission products (LLFPs): $^{79}$Se, $^{99}$Tc, $^{107}$Pd, $^{129}$I, $^{137}$Cs. Our comparative studies show that although the neutron production efficiency of the GF $γ$-ray beam (per MW of the beam power) is approximately $14$ times lower than that of the $500\,$MeV proton beam, the overall net ANES power production efficiency for the GF beam driver scheme could be comparable to that of the proton beam driver scheme, while providing additional transmutation capacity, not available for the proton beam driven scheme. It is suggested that the GF-based ANES could provide a viable solution for the efficient transmutation of LLFPs without isotopic separation.

physics.acc-ph↗

arXiv2021

Radioactive ion beam production at the Gamma Factory

A very intense gamma beam of the Gamma Factory facility proposed at CERN can be used to generate radioactive ion beams (RIBs) with high production yields and study the structure of exotic neutron-rich nuclei. The radioactive nuclides are generated via photo-fission in several actinide targets and thermalized in high-purity cryogenic helium, filling a gas cell which is enclosing the targets. Electric fields are used to extract heavy ions and form RIBs which can be sent to various selection and measurement stations. Estimates for the production and extraction yields of exotic neutron-rich nuclei with such a setup are provided. A study of the impact of space charge, build-up inside the gas cell, on the extraction properties is presented and it is demonstrated that the beam needs to be chopped for achieving optimal extraction yields.

nucl-ex↗

arXiv2020

High-luminosity Large Hadron Collider with laser-cooled isoscalar ion beams

This paper presents one of the case studies of the Gamma Factory initiative -- a proposal of a new operation scheme of ion beams in the CERN accelerator complex. Its goal is to extend the scope and precision of the LHC-based research by complementing the proton-proton collision programme with the high-luminosity nucleus-nucleus one. Its numerous physics highlights include studies of the exclusive Higgs-boson production in photon-photon collisions and precision measurements of the electroweak (EW) parameters. There are two principal ways to increase the LHC luminosity which do not require an upgrade of the CERN injectors: (1) modification of the beam-collision optics and (2) reduction of the transverse emittance of the colliding beams. The former scheme is employed by the ongoing high-luminosity (HL-LHC) project. The latter one, applicable only to ion beams, is proposed in this paper. It is based on laser cooling of bunches of partially stripped ions at the SPS flat-top energy. For isoscalar calcium beams, which fulfil the present beam-operation constrains and which are particularly attractive for the EW physics, the transverse beam emittance can be reduced by a factor of $5$ within the $8$ seconds long cooling phase. The predicted nucleon-nucleon luminosity of $L_{NN}= 4.2 \times 10^{34}\,$s$^{-1}$cm$^{-2}$ for collisions of the cooled calcium beams at the LHC top energy is comparable to the levelled luminosity for the HL-LHC proton-proton collisions, but with reduced pile-up background. The scheme proposed in this paper, if confirmed by the future Gamma Factory proof-of-principle experiment, could be implemented at CERN with minor infrastructure investments.

physics.acc-ph↗

arXiv2016

On the contribution of the double Drell-Yan process to WW and ZZ production at the LHC

In this paper we investigate consequences of an assumption that the discrepancy of the predicted and observed W+W- production cross sections at the LHC is caused by the missing contribution of the double Drell-Yan process (DDYP). Using our simple model of DDYP of Ref. [1] we show that inclusion of this production mechanism leads to a satisfactory, parameter-free description of the two-lepton mass distribution for 0-jet W+W- events and the four-lepton mass distribution for ZZ events. In such a scenario the Higgs-boson contribution is no longer necessary to describe the data. An experimental programme to prove or falsify such an assumption is proposed.

hep-ph↗

arXiv2016

QED radiative corrections and their impact on H -> tau tau searches at the LHC

In this paper we show that the excess of the tau tau events with respect to the Standard Model background predictions, observed by the ATLAS and CMS collaborations and interpreted as the evidence of the Higgs-boson decay into a pair of tau-leptons, may be accounted for by properly taking into account QED radiative corrections in the modelling of the Z/gamma* -> tau tau background.

hep-ph↗

arXiv2014

The LHC excess of four-lepton events interpreted as Higgs-boson signal: background from Double Drell--Yan process?

We construct a simple model of the Double Drell--Yan Process (DDYP) for proton--proton collisions and investigate its possible contribution to the background for the Higgs-boson searches at the LHC. We demonstrate that under the assumption of the predominance of short range, ${\cal O}(0.1)\,$fm, transverse-plane correlations of quark--antiquark pairs within the proton this contribution becomes important and may even explain the observed excess of the four-lepton events at the LHC -- the events interpreted as originating from the Higgs-boson decays: $ H \rightarrow ZZ^{*} \rightarrow 4l$ and $ H \rightarrow WW^{*} \rightarrow 2l 2 ν$.

hep-ph↗

arXiv2013

Numerical solution of the integral form of the resummed Balitsky-Kovchegov equation

The Balitsky--Kovchegov (BK) evolution equation in its resummed integral form as obtained in JHEP 1202 (2012) 117 and arXiv:1206.1223 is considered. We solve it numerically and compare to the unresummed BK equation formulated as an integral equation and to the solution obtained by the BKsolver package. Sensitivity of the solution to an introduced resolution parameter and initial conditions is investigated.

hep-ph↗

arXiv2013

Markov Chain Mote Carlo solution of BK equation through Newton-Kantorovich method

We propose a new method for Monte Carlo solution of non-linear integral equations by combining the Newton-Kantorovich method for solving non-linear equations with the Markov Chain Monte Carlo (MCMC) method for solving linear equations. The Newton-Kantorovich method allows to express the non-linear equation as a system of the linear equations which then can be treated by the MCMC (random walk) algorithm. We apply this method to the Balitsky-Kovchegov (BK) equation describing evolution of gluon density at low x. Results of numerical computations show that the MCMC method is both precise and efficient. The presented algorithm may be particularly suited for solving more complicated and higher-dimensional non-linear integral equation, for which traditional methods become unfeasible.

hep-ph↗

arXiv2009

WINHAC - the Monte Carlo event generator for single W-boson production in hadronic collisions

We present the Monte Carlo event generator WINHAC for the charged-current Drell-Yan process, i.e. single W-boson production with leptonic decays in hadronic collisions. It features multiphoton radiationwithin the Yennie-Frautschi-Suura exclusive exponentiation scheme with O(alpha) electroweak corrections. For the initial-state QCD/QED parton shower and hadronisation it is interfaced directly to PYTHIA. It implements the options for proton-proton, proton-antipronton and any nucleus-nucleus collisions. Moreover, it includes the polarized W-boson production and the neutral current Drell-Yan process, both at the Born level. Generation of weighted as well as unweighted (weight=1) events is possible. WINHAC has been thoroughly tested numerically and cross-checked with independent Monte Carlo programs, such as HORACE and SANC; in the so-called tuned comparisons, an agreement at the sub-permil-level has been reached. It has also been used as a basic tool for developing and testing some new measurement methods of the Standard Model parameters at the LHC.

hep-ph↗

arXiv2009

Prospect for precision measurements of MW+ -MW- & MW at the LHC: Shortcuts revisited

The claim that the W boson mass might be measured at the LHC with a precision of O(10 MeV) is critically reviewed. It is argued that such a precision cannot be achieved, unless a dedicated measurement program, specific to the LHC is pursued. We propose such a program. Its main target is to significantly improve the experimental control of the relative polarisation of the W+, W- and Z bosons. We propose to achieve this goal either by running dedicated isoscalar beams at the LHC or by running, in parallel to the standard p-p collision program, a dedicated muon scattering "LHC-support-experiment" at the CERN SPS. One of these auxiliary measurements is necessary for the "precision measurement program" at the LHC, but not sufficient. It must be followed by dedicated measurement strategies which are robust with respect to both the systematic measurement uncertainties and to the perturbative and non-perturbative QCD effects. We propose such strategies and evaluate their precision. At the LHC, contrary to the Tevatron case, both the masses of the W+ and of the W- bosons must be measured with high precision. In this context, we propose and evaluate LHC dedicated strategies to measure the difference of the masses of the W+ and W- bosons and of the absolute mass of the W boson assuming both masses are equal. We show how one can overcome the obstacles in measuring the masses of W+ and W- to a precision of 10 MeV. We present a detailed evaluation of the precision of the proposed methods based on the studies of a large, O(10^11), sample of simulated W and Z production events.

hep-ex↗

arXiv2002

Precision predictions for W-pair production at LEP2

Theoretical calculations for the W-pair production process at LEP2 in terms of Monte Carlo event generators RacoonWW and KorlaW&YFSWW3 are reviewed. The discussion concentrates on precision predictions for the main LEP2 WW observables. The theoretical precision of the above programs is estimated to be ~0.5% for the total WW cross section sigma_{WW}, ~5MeV for the W-boson mass M_W, and ~0.005 for the triple-gauge-boson coupling lambda = lambda_{gamma} = lambda_Z, which is sufficient for the final LEP2 data analyses.

hep-ph↗