arXiv subjects

Izabela Babiarz

Publications and source records attributed to Izabela Babiarz.

At least 19 recordsLinked to original sources

arXiv2026

Competition of $χ_{c}(2P)$ quarkonia and continuum in $e^+ e^- \to e^+ e^- D \bar{D}$

We discuss the production of $D \bar{D}$ pairs in $e^+ e^-$ collisions, where $D$ refers to either $D^0$ or $D^+$. The continuum mechanism with the $t/u$-channel vector-meson $D^*$ exchanges are considered. The results of the calculation depend on the parameter of the off-shell form-factor for the virtual $D^*$ mesons. The $D^* D γ$ coupling constants are found from the $D^* \to D γ$ decays. We find relatively large contribution for the $D^0 {\bar D}^0$ channel and much smaller contribution in the $D^+ D^-$ channel. In the second case we consider also the $D^{\pm}$ exchanges. We conclude that the bump at $M_{D^0 {\bar D}^0} = 3.8$ GeV observed by the Belle and BaBar Collaborations has rather continuum origin than it corresponds to the broad resonance $χ_{c0}(3860)$. We discuss also production of the $χ_{c2}(3930)$ resonance which is a candidate for the $χ_{c2}(2P)$ state. This state can decay into both $D \bar{D}$ channels, however the branching fractions are not well known at present. From a comparison of our model results to the BaBar data we find $B(χ_{c2}(3930) \to D \bar{D}) = 0.58 \pm 0.13$ using the two-photon width $Γ_{γγ} = 0.544$ keV (obtained for the Buchmüller-Tye potential) evaluated within the light-front approach (NRQCD limit). Our finding of $Γ_{γγ} \times B(χ_{c2}(3930) \to D \bar{D}) = 0.32 \pm 0.07$ keV is close to the Belle and BaBar results. Realistic predictions of the differential distributions in several variables and integrated cross-sections are given for the Belle II kinematics.

hep-ph↗

arXiv2026

Transition Form-Factor for $η_Q$ at NNLO in the strong coupling $α_s$ and with all-order $v^2$ resummation

In this work, we discuss both relativistic and perturbative QCD corrections to the transition form-factor ${\cal F}_{η_Q}{(t_1,t_2)}$ for the process $γ^*(q_1) γ^*(q_2) \leftrightarrow η_Q(P)$ with dependencies on the normalised photon virtualities $t_1=q_1^2/m_Q^2$ and $t_2=q_2^2/m_Q^2$, where $m_Q$ is the heavy quark mass. We resum a class of relativistic corrections to all orders in the relativistic parameter $\langle v^2 \rangle_{η_Q}$. In addition, we include perturbative QCD corrections up to Next-to-Next-to-Leading Order (NNLO) in the strong coupling constant $α_s$. This involves the computation of two-loop amplitudes with two off-shell photons. We explore three different phenomenological applications of our transition form-factors for the charmonium case. We first study the ratio $\vert {\cal F}_{η_c}{(t_1,0)} \vert/ \vert {\cal F}_{η_c}{(0,0)} \vert$ for the single space-like photon case and compare our results with the existing $η_c$ measurements from the BaBar collaboration. Secondly, we consider observables for the case of double space-like photons and discuss the impact of the different corrections. The NNLO corrections for this case are presented here for the first time in the literature. Finally, we revisit the decay width $Γ[η_c \rightarrow γγ]$ and compare it with the existing PDG value.

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arXiv2024

$χ_{c2}$ tensor meson transition form factors in the light front approach

We continue our work on the light-front formulation of quarkonium $γ^* γ$ transition form factors, extending the formalism to $J^{PC} = 2^{++}$ tensor meson states. We present an analysis of $γ^* γ\to χ_{c2}$ transition amplitude and the pertinent helicity form factors. Our relativistic formalism is based on the light-front quark-antiquark wave function of the quarkonium. We calculate the two-photon decay width as well as three independent $γ^* γ$ transition form factors for $J_z = 0,1,2$ as a function of photon virtuality $Q^2$. We compare our results for the two-photon decay width to the recently measured ones by the Belle and BES III collaborations. Even when including relativistic corrections, a very small $Γ(λ= 0)/Γ(λ= 2)\sim10^{-3}$ ratio is found which is beyond present experimental precision. We also present the form factors as a function of photon virtuality and compare them to the sparse experimental data on the so-called off-shell width. The formalism presented here can be used for other $2^{++}$ mesons, excited charmonia or bottomonia or even light $q \bar q$-mesons.

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arXiv2023

Exclusive $η_c$ production by $γ^{*} γ$ interactions in electron-ion collisions

One of the main goals of future electron-ion colliders is to improve our understanding of the structure of hadrons. In this letter, we study the exclusive $η_c$ production by $γ^{*} γ$ interactions in $eA$ collisions and demonstrate that future experimental analysis of this process can be used to improve the description of the $η_c$ transition form factor. The rapidity, transverse momentum and photon virtuality distributions are estimated considering the energy and target configurations expected to be present at the EIC, EicC and LHeC and assuming different predictions for the light-front wave function of the $η_c$ meson. Our results indicate that the electron-ion colliders can be considered an alternative to providing supplementary data to those obtained in $e^- e^+$ colliders.

hep-ph↗

arXiv2023

Probing the structure of $χ_{c1}(3872)$ with photon transition form factors

We propose to study the structure of the enigmatic $χ_{c1}(3872)$ axial vector meson through its $γ^*_L γ\to χ_{c1}(3872)$ transition form factor. We derive a light-front wave function representation of the form factor for the lowest $c \bar c$ Fock-state. We found that the reduced width of the state is well within the current experimental bound recently published by the Belle collaboration. This strongly suggests a crucial role of the $c \bar c$ Fock-state in the photon-induced production. Our results for the $Q^2$ dependence can be tested by future single tagged $e^+ e^-$ experiments, giving further insights into the short-distance structure of this meson.

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arXiv2022

Proceedings of the IFJ PAN Particle Physics Summer Student Alumni Conference 2022

IFJ PAN PPSS Alumni Conference is organized by the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN). It is addressed to: participants of previous editions of Particle Physics Summer Student Programme, attendees of current PPSS edition and students interested in cooperation with IFJ PAN. First IFJ PAN Particle Physics Summer Student Alumni Conference was held on 9-10 July 2022, with topic focused on, but not restricted to, high energy physics.

hep-ex↗

arXiv2022

Light-front approach to axial-vector quarkonium $γ^* γ^*$ form factors

In this work, we perform a detailed study of transition form factors for axial-vector meson production via the two-photon fusion process $γ^* γ^* \to 1^{++}$, with space-like virtual photons in the initial state and a $P$-wave axial-vector quarkonium in the final state. In this analysis, we employ the formalism of light-front quarkonium wave functions obtained from a solution of the Schrödinger equation for a selection of interquark potentials for $Q \bar Q$ interaction. We found the helicity structure and covariant decomposition of the matrix elements that can be generically applied for any $q \bar q$ axial-vector meson $γ^* γ^* \to 1^{++}$ transition, while our numerical results are given for the phenomenologically relevant charmonium $χ_{c1}$ state. We present the helicity form factors as functions of both photon virtualities. We also obtain, that $Q F_{\rm LT}(Q^2,0)/F_{\rm TT}(Q^2,0) = {\rm const.}$

hep-ph↗

arXiv2021

Central exclusive production of $η_c$ and $χ_{c0}$ in the light-front k$_{\perp}$-factorization approach

We study the exclusive production of $J^{PC}=0^{++}, 0^{--}$ charmonium states in proton-proton collisions at the LHC energies The $pp \to ppη_c$ reaction is discussed for the first time. We observe a substantial contribution from the nonperturbative domain of gluon virtualities, especially for $η_c$ production. To model the nonperturbative region better, we utilize models of the unintegrated gluon distribution based on parametrizations of the color dipole cross-section.

hep-ph↗

arXiv2021

Prompt hadroproduction of C-even quarkonia in the light-front $k_T$ -factorization approach

We present a new approach for the prompt production of quarkonia which is based on the $k_T$-factorization method. The production of even C-parity quarkonia proceeds via the fusion of two (off-shell) gluons. Especially in the kinematics of the LHCb experiment these processes are thus expected to be a sensitive probe of the small-$x$ gluon distribution. We calculate the relevant off-shell matrix elements in terms of the light-front wave functions of the quarkonium states. We present our results for scalar and pseudoscalar charmonia and discuss photon transition form factors as well as cross sections for prompt hadroproduction. We compare our results for the $η_c$ to recent LHCb data.

hep-ph↗

arXiv2020

Production of $η_{c}(1S,2S)$ in $e^+ e^-$ and $pp$ collisions

We derive the light-front wave function (LFWF) representation of the $γ^{\star} γ^{\star} \to η_{c} (1S),η_{c}(2S)$ transition form factor $F(Q^2_1,Q^2_2)$ for two virtual photons in the initial state. For the LFWF, we use different models obtained from the solution of the Schrödinger equation for a variety of $c\bar{c}$ potentials. We compare our results to the BaBar experimental data for the $η_{c}(1S)$ transition form factor, for one real and one virtual photon. We observe that the onset of the asymptotic behaviour is strongly delayed and discuss applicability of the collinear and/or massless limit. In addition, we present a thorough analysis of $η_{c}(1S,2S)$ quarkonia hadroproduction in $k_{\perp}$-factorisation in the framework of the light-front potential approach for the quarkonium wave function. The off-shell matrix elements for the $g^{\star} g^{\star} \to η_{c} (1S,2S)$ vertices are derived. We discuss the importance of taking into account the gluon virtualities. We present the transverse momentum distributions of $η_c$ for several models of the unintegrated gluon distributions. Our calculations are performed for four distinct parametrizations for the $c\bar{c}$ interaction potential consistent with the meson spectra. We compare our results for $η_{c}(1S)$ to measurements by the LHCb collaboration and present predictions for $η_{c}(2S)$ production.

hep-ph↗

arXiv2020

Central exclusive production of scalar and pseudoscalar charmonia in the light-front $k_T$-factorization approach

We study exclusive production of scalar $χ_{c0}\equiv χ_c(0^{++})$ and pseudoscalar $η_c$ charmonia states in proton-proton collisions at the LHC energies. The amplitudes for $gg \to χ_{c0}$ as well as for $gg \to η_c$ mechanisms are derived in the $k_{T}$-factorization approach. The $p p \to p p η_c$ reaction is discussed for the first time. We have calculated rapidity, transverse momentum distributions as well as such correlation observables as the distribution in relative azimuthal angle and $(t_1,t_2)$ distributions. The latter two observables are very different for $χ_{c0}$ and $η_c$ cases. In contrast to the inclusive production of these mesons considered very recently in the literature, in the exclusive case the cross section for $η_c$ is much lower than that for $χ_{c0}$ which is due to a special interplay of the corresponding vertices and off-diagonal UGDFs used to calculate the cross sections. We present the numerical results for the key observables in the framework of potential models for the light-front quarkonia wave functions. We also discuss how different are the absorptive corrections for both considered cases.

hep-ph↗

arXiv2020

Hadroproduction of scalar $P$-wave quarkonia in the light-front $k_T$-factorization approach

In this work, we present a thorough analysis of scalar $P$-wave $χ_{Q0}$, $Q=c,b$ quarkonia electromagnetic form factors for the $γ^* γ^* \to χ_{Q0}$ couplings, as well as their hadroproduction observables in $k_\perp$-factorisation using the light-front potential approach for the quarkonium wave function. The electromagnetic form factors are presented as functions of photon virtualities. We discuss the role of the Melosh spin-rotation and relativistic corrections estimated by comparing our results with those in the standard nonrelativistic QCD (NRQCD) approach. Theoretical uncertainties of our approach are found by performing the analysis with two different unintegrated gluon densities and with five distinct models of the $Q\bar Q$ interaction potentials consistent with the meson spectra. The results for the rapidity and transverse momentum distributions of $χ_{Q0}$ produced in high-energy $pp$ collisions at $\sqrt{s} = 13 \, \rm{TeV}$ are shown.

hep-ph↗

arXiv2019

Prompt hadroproduction of $η_c(1S,2S)$ in the $k_T$-factorization approach

In this work, we present a thorough analysis of $η_c(1S,2S)$ quarkonia hadroproduction in $k_\perp$-factorisation in the framework of the light-front potential approach for the quarkonium wave function. The off-shell matrix elements for the $g^* g^* η_c(1S,2S)$ vertices are derived. We discuss the importance of taking into account the gluon virtualities. %We discuss the role of relativistic corrections, the Melosh spin-rotation and theoretical uncertainties by comparing our results with the standard NRQCD approach. We present the transverse momentum distributions of $η_c$ for several models of the unintegrated gluon distributions. Our calculations are performed for four distinct parameterisations for the $c\bar c$ interaction potential consistent with the meson spectra. We compare our results for $η_c(1S)$ to measurements by the LHCb collaboration and present predictions for $η_c(2S)$ production.

hep-ph↗

arXiv2019

Production asymmetry of $ν_τ$ neutrinos and ${\overline ν}_τ$ antineutrinos from a fixed target experiment SHiP

We discuss how to calculate cross sections as well as rapidity, transverse momentum and energy distributions of $ν_τ$ and ${\overline ν}_τ$ produced from the direct $D_s^{\pm} \to ν_τ/{\overline ν}_τ$ and chain $D_s^{\pm} \to τ^+/τ^- \to ν_τ/{\overline ν}_τ$ decays in $p\!+^{96}\!\mathrm{Mo}$ scattering with proton beam $E_{\mathrm{lab}}$ = 400 GeV \textit{i.e.} at $\sqrt{s}_{NN}$ = 27.4 GeV. The $τ$ decays are simulated with the help of the \textsc{Tauola} code and include multiple decay channels of $τ$ in amounts proportional to their branching ratios. In our calculations we include $D_s^{\pm}$ from charm fragmentation $c \to D_s^{+}$ and $\bar c \to D_s^-$ as well as those from subleading fragmentation of strange quarks/antiquarks $s \to D_s^-$ and $\bar s \to D_s^+$. The $s \ne \bar s$ asymmetry of the strange quark content of proton is included. The different contributions to $D_s^{\pm}$ and $ν_τ / {\overline ν}_τ$ are shown explicitly. We discuss and quantify a not discussed so far effect of asymmetries for production of $ν_τ$ and ${\overline ν}_τ$ caused by subleading fragmentation mechanism and discuss related uncertainties. A potential measurement of the asymmetry is discussed. Estimates of a number of observed $ν_τ / \overlineν_τ$ in the $ν_τ / \overlineν_τ +^{208}\!\mathrm{Pb}$ reaction, with 2m long target are given with the help of the NuWro program. We refer also to the production of the high-energy (anti)neutrinos in the atmosphere.

hep-ph↗

arXiv2019

The ${γ^* γ^* \to η_c (1S,2S)}$ transition form factors for spacelike photons

We derive the light-front wave function (LFWF) representation of the $γ^* γ^* \to η_c(1S)\,,η_c(2S)$ transition form factor $F(Q_1^2, Q_2^2)$ for two virtual photons in the initial state. For the LFWF, we use different models obtained from the solution of the Schrödinger equation for a variety of $c \bar c$ potentials. We compare our results to the BaBar experimental data for the $η_c(1S)$ transition form factor, for one real and one virtual photon. We observe that the onset of the asymptotic behaviour is strongly delayed and discuss applicability of the collinear and/or massless limit. We present some examples of two-dimensional distributions for $F (Q_1^2,Q_2^2)$. A factorization breaking measure is proposed and factorization breaking effects are quantified and shown to be almost model independent. Factorization is shown to be strongly broken, and a scaling of the form factor as a function of $\bar Q^2 = (Q_1^2 + Q_2^2)/2$ is obtained.

hep-ph↗

arXiv2019

Associated production of $χ_c$ pairs with a gluon in the collinear-factorization approach

We calculate cross section for production of $χ_c$ pairs in proton-proton collisions. The cross section for the $g g \to χ_{c J_1} χ_{c J_2}$ is considerably smaller (especially for $χ_{c 1} χ_{c 1}$ final state) than that obtained recently in the $k_T$-factorization approach. We calculate therefore next-to-leading order contributions with $χ_c$ pair and one extra associated (mini-)jet. We find these contributions to be much larger than those for the $2 \to 2$ contribution. Especially the emission of a leading gluon (carrying a large momentum fraction of one of the incoming gluons) are important. These emissions in the $k_T$-factorization approach are absorbed into the initial state unintegrated gluon distributions. A smaller contribution to the cross section comes from the production of central gluons emitted with rapidities between the $χ_c$-mesons. They do lead, however, to an enhancement of the $χ_c$-pair production at large rapidity distance between the mesons. Our present study explains the size of the cross section for the $χ_c$ pair production obtained previously in the $k_T$-factorization approach. Several differential distributions are presented.

hep-ph↗

arXiv2017

Rescattering effects in jet-gap-jet processes

We discuss the process of colour-singlet parton-parton scattering, which in hadron-hadron collision can lead to production of jet events, where a rapidity gap between the jets is present. The dynamics of the process is calculated within LL BFKL approximation. Using Pythia MC generator, hadronic shapes of jet-gap-jet events are studied, in particular the distributions of the rapidity gap size resulting from the jet formation processes. Using Pythia's modelling of multiple parton interactions, the rescattering effects are simulated. It is shown how these effects influence the gap size distributions. The kinematic dependence of the gap survival probability is discussed.

hep-ph↗

arXiv2017

Single-diffractive production of dijets within the $k_t$-factorization approach

We discuss single-diffractive production of dijets. The cross section is calculated within the resolved pomeron picture, for the first time in the $k_t$-factorization approach, neglecting transverse momentum of the pomeron. We use Kimber-Martin-Ryskin unintegrated parton (gluon, quark, antiquark) distributions (UPDF) both in the proton as well as in the pomeron or subleading reggeon. The UPDFs are calculated based on conventional MMHT2014nlo PDFs in the proton and H1 collaboration diffractive PDFs used previously in the analysis of diffractive structure function and dijets at HERA. For comparison we present results of calculations performed within collinear-factorization approach. Our results remaind those obtained in the NLO approach. The calculation is (must be) supplemented by the so-called gap survival factor which may, in general, depend on kinematical variables. We try to describe the existing data from Tevatron and make detailed predictions for possible LHC measurements. Several differential distributions are calculated. The $\overline{E}_T$, $\overlineη$ and $x_{\bar p}$ distributions are compared with the Tevatron data. A reasonable agreement is obtained for the first two distributions. The last one requires to introduce a gap survival factor which depends on kinematical variables. We discuss how the phenomenological dependence on one kinematical variable may influence dependence on other variables such as ${\overline E}_T$ and ${\overline η}$. Several distributions for the LHC are shown.

hep-ph↗