arXiv subjects

Michal Praszalowicz

Publications and source records attributed to Michal Praszalowicz.

At least 37 records · Page 2Linked to original sources

arXiv2018

Exotic interpretation of $Ω_c$ excited states

We use the chiral quark-soliton model to interpret five excited $Ω_c$ states recently reported by the LHCb collaboration and confirmed by Belle. We briefly recapitulate the model and its application to light baryons. We then show how the model can be extended to the case of baryons with one heavy quark. We test the model against ground state heavy baryons and then examine possible excitations. We argue that it is not possible to accommodate all five $Ω_c$'s within five parity minus excitations predicetd by the model and propose to interpret two narrowest states split by 70 MeV as pentaquarks belonging to the SU(3) representation $\overline{15}$.

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arXiv2017

Strong decays of exotic and non-exotic heavy baryons in the chiral quark-soliton model

In the large $N_c$ limit both heavy and light baryons are described by the universal mean field, which allows us to relate the properties of heavy baryons to light ones. With the only input from the decays of light octet baryons (due to the universality of the chiral mean field), excellent description of strong decays of both charm and bottom sextets is obtained. The parameter-free prediction for the widths of exotic anti-decapentaplet ($\overline{\boldsymbol{15}}$) baryons is also made. The exotic heavy baryons should be anomalously narrow despite of large phase space available. In particular, the widths of $Ω_c(3050)$ and $Ω_c(3119)$, interpreted as members of $\overline{\boldsymbol{15}}$-plet, are very small: 0.48~MeV and 1.12~MeV respectivly. This result is in very good agreement with the measurements of the LHCb Collaboration and provides natural and parameter free explanation of the LHCb observation that $Ω_c(3050)$ and $Ω_c(3119)$ have anomalously small widths among five recently observed states.

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arXiv2017

On a possibility of baryonic exotica

Models based on chiral symmetry predict pentaquarks that have relatively low masses. We briefly review both theoretical and experimental status of exotica in the light sector. Next, shall show how to extend chiral models to baryons with one heavy quark and show that one expects exotica also in this case. Finally, we interpret recently discovered by the LHCb collaboration five $Ω^*_c$ resonances in terms of regular and exotic excitations of the ground state $Ω_c$.

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arXiv2016

Saturation and geometrical scaling

We discuss emergence of geometrical scaling as a consequence of the nonlinear evolution equations of QCD, which generate a new dynamical scale, known as the saturation momentum: Qs. In the kinematical region where no other energy scales exist, particle spectra exhibit geometrical scaling (GS), i.e. they depend on the ratio pT=Qs, and the energy dependence enters solely through the energy dependence of the saturation momentum. We confront the hypothesis of GS in different systems with experimental data.

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arXiv2016

Saturation and geometrical scaling in small systems

Saturation and geometrical scaling (GS) of gluon distributions are a consequence of the non-linear evolution equations of QCD. We argue that in pp GS holds for the inelastic cross-section rather than for the multiplicity distributions. We also discuss possible fluctuations of the proton saturation scale in pA collisions at the LHC.

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arXiv2016

Fluctuations and the rapidity dependence of charged particles spectra in fixed centrality bins in p$A$ collisions

We argue that large fluctuations in the saturation momentum are necessary to explain the ATLAS and ALICE data on pA collisions measured at the LHC. Using a form for the distribution of fluctuations motivated by theoretical studies of the non-linear evolution equations for the Color Glass Condensate, we find a remarkably good agreement between theory and the measured distributions. If the saturation momentum fluctuates, we argue that the cross section for a proton probe should also fluctuate, consistent with previous observations. Finally we discuss these results and their possible consistency with what is known about multiplicity fluctuations in such collisions, and attempts to describe the ridge effect from properties of the initial state.

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arXiv2016

Saturation and geometrical scaling -- from small $x$ deep inelastic ep scattering to high energy proton-proton and heavy ion collisions

Gluon distributions of colliding hadrons saturate as a result of the non-linear evolution equations of QCD. As a consequence there exists the so called saturation momentum, which is related to the gluon density per unit rapidity per transverse area. When saturation momentum is the only scale for physical processes, different observables exhibit geometrical scaling (GS). We show a number of examples of GS and its violation in different reactions.

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arXiv2015

Geometrical Scaling in Inelastic Inclusive Particle Production at the LHC

Analyzing recent ALICE data on inelastic pp scattering at the LHC energies we show that charged particle distributions exhibit geometrical scaling (GS). We show also that the inelastic cross-section is scaling as well and that in this case the quality of GS is better than for multiplicities. Moreover, exponent $λ$ characterizing the saturation scale is for the cross-section scaling compatible with the one found in deep inelastic ep scattering at HERA. Next, by parametrizing charged particles distributions by the Tsallis-like formula, we find a somewhat unexpected solution that still exhibits GS, but differs from the "standard" one where the Tsallis temperature is proportional to the saturation scale.

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arXiv2015

On the longitudinal structure function in the dipole model

We compare new HERA data for the longitudinal structure function $F_{\rm L}$ with the predictions of different variants of the dipole model. In particular we show that the ratio $F_{\rm L}/F_2$ is well described by the dipole models and is rather insensitive to the details of the fit. Fits to $F_2$ are performed with the help of geometrical scaling (GS). Using the property of GS we derive the bounds for $F_{\rm L}/F_2$ both for the different versions of the dipole model and in the general case. Finally we briefly discuss how the higher Fock components of the photon wave function may affect these bounds.

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arXiv2015

Saturation and Geometrical Scaling: from Deep Inelastic ep Scattering to Heavy Ion Collisions

Saturation of gluon distribution is a consequence of the non-linear evolution equations of QCD. Saturation implies the existence of so called saturation momentum which is defined as a gluon density per unit rapidity per transverse area. At large energies for certain kinematical domains saturation momentum is the only scale for physical processes. As a consequence different observables exhibit geometrical scaling (GS). We discuss a number of examples of GS in different reactions.

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arXiv2014

Geometrical Scaling and the Dependence of the Average Transverse Momentum on the Multiplicity and Energy for the ALICE Experiment

We review the recent ALICE data on charged particle multiplicity in p-p collisions, and show that it exhibits Geometrical Scaling (GS) with energy dependence given with characteristic exponent $λ=0.22$. Next, starting from the GS hypothesis and using results of the Color Glass Condensate effective theory, we calculate $< p_{\text{T}}>$ as a function $N_{\rm ch}$ including dependence on the scattering energy $W$. We show that $< p_{\text{T}}>$ both in p-p and p-Pb collisions scales in terms of scaling variable $(W/W_{0})^{λ/(2+λ)}% \sqrt{N_{\mathrm{ch}}/S_{\bot}}$ where $S_{\bot}$ is multiplicity dependent interaction area in the transverse plane. Furthermore, we discuss how the behavior of the interaction radius $R$ at large multiplicities affects the mean $p_{\mathrm{T}}$ dependence on $N_{\rm ch}$, and make a prediction that $< p_{\text{T}}>$ at high multiplicity should reach an energy independent limit.

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arXiv2014

Why mean $p_{\rm T}$ is interesting

We discuss energy dependence of mean $p_{\rm T}$ correlation with $N_{\rm ch}$ basing on general features of high energy collisions such as saturation and geometrical scaling. We use Color Glass Condensate calculation of an effective interaction radius that scales as a third root of multiplicity, and then saturates. With this model input we construct scaling variable for $< p_{\rm T} > (N_{\rm ch})$ at different energies both for pp and pPb collisions, and show that recent ALICE data indeed does exhibit this scaling property. We discuss energy dependence of the interaction radius and argue that since the radius cannot grow too large, a universal behavior of $< p_{\rm T} >$ for large multiplicities is expected.

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arXiv2014

Geometrical scaling and its breaking in high energy collisions

We report on recent analyses of different pieces of data, which exhibit Geometrical Scaling (GS) and its breaking. GS is a consequence of the existence of an intermediate energy scale, called saturation momentum, and allows to relate data at different energies, of different systems and also at different multiplicities and/or centralities.

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arXiv2013

Geometrical scaling for identified particles

We show that recently measured transverse momentum spectra of identified particles exhibit geometrical scaling (GS) in scaling variable $τ_{\tilde{m}_{\rm T}}=(\tilde{m}_{\rm T}/Q_0)^{2} (\tilde{m}_{\rm T}/ W)^λ$ where $\tilde{m}_{\rm T}=\sqrt{m^2+p^2_{\rm T}}-m$. We explore consequences of GS and show that both mid rapidity multiplicity and mean transverse momenta grow as powers of scattering energy. Furthermore, assuming Tsallis-like parametrization of the spectra we calculate the coefficients of this growth. We also show that Tsallis temperature is related to the average saturation scale.

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arXiv2013

Emergence and violation of geometrical scaling in pp collisions

We argue that geometrical scaling (GS) proposed originally in the context of Deep Inelastic Scattering (DIS) at HERA works also in pp collisions at the LHC energies and in NA61/SHINE experiment. We show that in DIS GS is working up to relatively large Bjorken $x \sim 0.1$. As a consequence negative pion multiplicity $p_{\rm T}$ distributions at NA61/SHINE energies exhibit GS in mid rapidity region. For $y \ne 0$ clear sign of scaling violations can be seen when one of the colliding partons has Bjorken $x \ge 0.1$. Finally, we argue that in the case of identified particles GS scaling is still present but the scaling variable is a function of transverse mass rather than $p_{\rm T}$.

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arXiv2013

Transverse Momentum of Protons, Pions and Kaons in High Multiplicity pp and pA Collisions: Evidence for the Color Glass Condensate?

The CMS experiment at the Large Hadron Collider has recently presented data on the average transverse momentum of protons, kaons and pions as a function of particle multiplicity. We relate the particle multiplicity to saturation momentum using recently published computations of the interaction radius determined from the theory of the Color Glass Condensate. We show that the pp and the pA experimental data scale in terms of these saturation momenta. Computing transverse momentum spectra for identified particles using Boltzmann-type distributions and relating different associated multiplicities using geometric scaling, these simple distributions reproduce the observed dependence of the mean transverse momentum on particle multiplicities seen in both pp and pA interactions for pions to good accuracy, and to fair agreement for protons and kaons.

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arXiv2013

Violation of Geometrical Scaling in pp Collisions at NA61/SHINE

We analyze geometrical scaling (GS) of negative pion multiplicity p_T distributions at NA61/SHINE energies. We show that even though NA61/SHINE energies are low, one may expect to find GS in the particle spectra. We argue that qualitative behavior of ratios of multiplicities at different energies is in agreement with a simple picture of GS which is violated for p_T smaller than some nonperturbative scale Lambda and when larger Bjorken x of one of the scattering patrons crosses x_max above which gluonic cloud becomes dilute and quark degrees of freedom become important.

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arXiv2013

Geometrical scaling in high energy collisions and its breaking

We analyze geometrical scaling (GS) in Deep Inelstic Scattering at HERA and in pp collisions at the LHC energies and in NA61/SHINE experiment. We argue that GS is working up to relatively large Bjorken $x \sim 0.1$. This allows to study GS in negative pion multiplicity $p_{\rm T}$ distributions at NA61/SHINE energies where clear sign of scaling violations is seen with growing rapidity when one of the colliding partons has Bjorekn $x \ge 0.1$.

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