0000000000994482
AUTHOR
Valery E. Lyubovitskij
showing 40 related works from this author
K− over K+ multiplicity ratio for kaons produced in DIS with a large fraction of the virtual-photon energy
2018
The K$^{-}$ over K$^{+}$ multiplicity ratio is measured in deep-inelastic scattering, for the first time for kaons carrying a large fraction $z$ of the virtual-photon energy. The data were obtained by the COMPASS collaboration using a 160 GeV muon beam and an isoscalar $^6$LiD target. The regime of deep-inelastic scattering is ensured by requiring $Q^2>1$ (GeV/$c)^2$ for the photon virtuality and $W>5$ GeV/$c^2$ for the invariant mass of the produced hadronic system. Kaons are identified in the momentum range from 12 GeV/$c$ to 40 GeV/$c$, thereby restricting the range in Bjorken-$x$ to $0.010.75$. For very large values of $z$, $i.e.$ $z>0.8$, we observe the kaon multiplicity ratio to fall …
Physical observables in the decay Λb→Λc(→Λ+π)+τ−+ν̄τ
2015
We analyze the tauonic semileptonic baryon decays [Formula: see text] with particular emphasis on the lepton helicity flip contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization components of the [Formula: see text] and the [Formula: see text], and the lepton-side forward-backward asymmetries. We use the covariant confined quark model to provide numerical results on these observables.
One-Pion Charm Baryon Transitions in a Relativistic Three-Quark Model
1998
We study one-pion transitions between charm baryon states in the framework of a relativistic three-quark model. We calculate the charm baryon-pion coupling factors that govern the S-wave, P-wave and D-wave one-pion transitions from the s-wave and the lowest lying p-wave charm baryon states down to the s-wave charm baryon states. For these we obtain: g_{\Sigma_c\Lambda_c\pi}=8.88 GeV^{-1}, f_{\Lambda_{c1}\Sigma_c\pi}=0.52 and f_{\Lambda_{c1}^*\Sigma_c\pi}=21.5 GeV^{-2}. We compare our rate predictions for the one-pion transitions with experimental results.
Charm and bottom baryon decays in the Bethe-Salpeter approach: Heavy to heavy semileptonic transitions
1998
Charm and bottom baryons and mesons are studied within the framework of a relativistically covariant 3D reduction of the Bethe-Salpeter equation. We carry out an analysis of semileptonic decays of heavy hadrons within this framework using explicit oscillator-type wave functions where we calculate Isgur-Wise functions, decay rates and asymmetry parameters. Within this model we also study the effect of interactions between the light quarks inside the heavy baryon and how they affect the values of the computed heavy baryon observables. We also elaborate on the role of relativistic effects in the calculation of the heavy baryon Isgur-Wise function.
Magnetic moments of heavy baryons in the relativistic three-quark model
2006
The magnetic moments of ground state single, double and triple heavy baryons containing charm or bottom quarks are calculated in a relativistic three-quark model, which, in the heavy quark limit, is consistent with Heavy Quark Effective Theory and Heavy Hadron Chiral Perturbation Theory. The internal quark structure of baryons is modeled by baryonic three-quark currents with a spin-flavor structure patterned according to standard covariant baryonic wave functions and currents used in QCD sum rule calculations.
Semileptonic decaysΛc+→Λℓ+νℓ(ℓ=e,μ)in the covariant quark model and comparison with the new absolute branching fraction measurements of Belle and BES…
2016
We present precise theoretical predictions for the absolute branching fractions of ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}(\ensuremath{\ell}=e,\ensuremath{\mu})$ decays in the covariant confined quark model. This study is motivated by two recent and accurate measurements of the absolute branching fractions of ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}{e}^{+}{\ensuremath{\nu}}_{e}$ by the Belle Collaboration at the KE…
Contribution of exclusive diffractive processes to the measured azimuthal asymmetries in SIDIS
2019
Hadron leptoproduction in Semi-Inclusive measurements of Deep-Inelastic Scattering (SIDIS) on unpolarised nucleons allows one to get information on the intrinsic transverse momentum of quarks in a nucleon and on the Boer-Mulders function through the measurement of azimuthal modulations in the cross section. These modulations were recently measured by the HERMES experiment at DESY on proton and deuteron targets, and by the COMPASS experiment using the CERN SPS muon beam and a $^6$LiD target. In both cases, the amplitudes of the $\cos\phi_h$ and $\cos 2\phi_h$ modulations show strong kinematic dependences for both positive and negative hadrons. It has been known since some time that the measu…
Ab initio three-loop calculation of the W -exchange contribution to nonleptonic decays of double charm baryons
2019
We have made an ab initio three-loop quark model calculation of the $W$-exchange contribution to the nonleptonic two-body decays of the doubly charmed baryons $\Xi_{cc}^{++}$ and $\Omega_{cc}^{+}$. The $W$-exchange contributions appear in addition to the factorizable tree graph contributions and are not suppressed in general. We make use of the covariant confined quark model previously developed by us to calculate the tree graph as well as the $W$-exchange contribution. We calculate helicity amplitudes and quantitatively compare the tree graph and $W$-exchange contributions. Finally, we compare the calculated decay widths with those from other theoretical approaches when they are available.
Relativistic constituent quark model with infrared confinement
2009
We refine the relativistic constituent quark model developed in our previous papers to include the confinement of quarks. It is done, first, by introducing the scale integration in the space of alpha-parameters, and, second, by cutting this scale integration on the upper limit which corresponds to an infrared cutoff. In this manner one removes all possible thresholds presented in the initial quark diagram. The cutoff parameter is taken to be the same for all physical processes. We adjust other model parameters by fitting the calculated quantities of the basic physical processes to available experimental data. As an application, we calculate the electromagnetic form factors of the pion and t…
Decay chain information on the newly discovered double charm baryon state $\Xi_{cc}^{++}$
2017
We interprete the new double charm baryon state found by the LHCb Collaboration in the invariant mass distribution of the set of final state particles $(\Lambda_c^+\,K^-\,\pi^+\,\pi^+)$ as being at the origin of the decay chain $\Xi_{cc}^{++} \to \Sigma_c^{++} (\to \Lambda_c^+ \pi^+) +\bar K^{*0} (\to K^- \pi^+)$. The nonleptonic decay $\Xi_{cc}^{++} \to \Sigma_c^{++} + \bar K^{*0}$ belongs to a class of decays where the quark flavor composition is such that the decay proceeds solely via the factorizing contribution precluding a contamination from internal $W$-exchange. We use the covariant confined quark model previously developed by us to calculate the four helicity amplitudes that descri…
Heavy-to-light semileptonic decays ofΛbandΛcbaryons in the covariant confined quark model
2014
We present a detailed analysis of the heavy-to-light semileptonic decays of theb andc baryons �b → pl ¯ νl andc → nl + νl in the covariant confined quark model. We calculate the invariant and helicity amplitudes of the two processes which are then used to analyze their angular decay distributions, their rates and asymmetry parameters.
Exclusive nonleptonic decays of bottom and charm baryons in a relativistic three-quark model: Evaluation of nonfactorizing diagrams
1998
Exclusive nonleptonic decays of bottom and charm baryons are studied within a relativistic three-quark model with a Gaussian shape for the momentum dependence of the baryon-three-quark vertex. We include factorizing as well as nonfactorizing contributions to the decay amplitudes. For heavy-to-light transitions Q -> q u d the total contribution of the nonfactorizing diagrams amount up to approximately 60% of the factorizing contributions in amplitude, and up to approximately 30% for b -> c u d transitions. We calculate the rates and the polarization asymmetry parameters for various nonleptonic decays and compare them to existing data and to the results of other model calculations.
Heavy Baryon Transitions in a Relativistic Three-Quark Model
1996
Exclusive semileptonic decays of bottom and charm baryons are considered within a relativistic three-quark model with a Gaussian shape for the baryon-three-quark vertex and standard quark propagators. We calculate the baryonic Isgur-Wise functions, decay rates and asymmetry parameters.
Antiproton over proton and K$^-$ over K$^+$ multiplicity ratios at high $z$ in DIS
2020
The $\bar{\rm p} $ over p multiplicity ratio is measured in deep-inelastic scattering for the first time using (anti-) protons carrying a large fraction of the virtual-photon energy, $z>0.5$. The data were obtained by the COMPASS Collaboration using a 160 GeV muon beam impinging on an isoscalar $^6$LiD target. The regime of deep-inelastic scattering is ensured by requiring $Q^2$ > 1 (GeV/$c$)$^2$ for the photon virtuality and $W > 5$ GeV/$c^2$ for the invariant mass of the produced hadronic system. The range in Bjorken-$x$ is restricted to $0.01 < x < 0.40$. Protons and antiprotons are identified in the momentum range $20 ��60$ GeV/$c$. In the whole studied $z$-region, the $\…
Analysis of the semileptonic and nonleptonic two-body decays of the double heavy charm baryon states Ξcc++,Ξcc+ and Ωcc+
2019
We calculate the semileptonic and a subclass of sixteen nonleptonic two-body decays of the double charm baryon ground states Ξcc++,Ξcc+ and Ωcc+ where we concentrate on the nonleptonic decay modes. We identify those nonleptonic decay channels in which the decay proceeds solely via the factorizing contribution precluding a contamination from W exchange. We use the covariant confined quark model previously developed by us to calculate the various helicity amplitudes which describe the dynamics of the 1/2+→1/2+ and 1/2+→3/2+ transitions induced by the Cabibbo-favored effective (c→s) and (d→u) currents. We then proceed to calculate the rates of the decays as well as polarization effects and ang…
Analysis of the nonleptonic two-body decays of the Λ hyperon
2021
We systematically study two-body nonleptonic decays of light lambda hyperon $\Lambda \to p \pi^- (n\pi^0)$ with account for both short- and long-distance effects. The short-distance effects are induced by five topologies of external and internal weak $W^\pm$ exchange, while long-distance effects are saturated by an inclusion of the so-called pole diagrams with intermediate $\frac{1}{2}^+$ and $\frac{1}{2}^-$ baryon resonances. The contributions from $\frac12^+$ resonances are calculated straightforwardly by account for nucleon and $\Sigma$ baryons whereas the contributions from $\frac{1}{2}^-$ resonances are calculated by using the well-known soft-pion theorem in the current-algebra approac…
Longitudinal double-spin asymmetry A1p and spin-dependent structure function g1p of the proton at small values of x and Q2
2018
Abstract We present a precise measurement of the proton longitudinal double-spin asymmetry A 1 p and the proton spin-dependent structure function g 1 p at photon virtualities 0.006 ( GeV / c ) 2 Q 2 1 ( GeV / c ) 2 in the Bjorken x range of 4 × 10 − 5 x 4 × 10 − 2 . The results are based on data collected by the COMPASS Collaboration at CERN using muon beam energies of 160 GeV and 200 GeV . The statistical precision is more than tenfold better than that of the previous measurement in this region. In the whole range of x , the measured values of A 1 p and g 1 p are found to be positive. It is for the first time that spin effects are found at such low values of x .
Rare baryon decaysΛb→Λℓ+ℓ−(ℓ=e,μ,τ) andΛb→Λγ: Differential and total rates, lepton- and hadron-side forward-backward asymmetries
2013
Using the covariant constituent quark model previously developed by us, we calculate the differential rate and the forward-backward asymmetries on the lepton and hadron side for the rare baryon decays ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$, $\ensuremath{\tau}$) and ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}\ensuremath{\gamma}$. We use helicity methods to write down a threefold joint angular decay distribution for the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\…
Heavy baryons in the relativistic quark model
2003
Abstract We present a summary of results for exclusive decays of single and double heavy-flavored baryons in the relativistic three-quark model.
Zb(10610) and Zb′(10650) decays in a covariant quark model
2017
We present a calculation of the strong decays of the exotic states ${Z}_{b}(10610)$ and ${Z}_{b}^{\ensuremath{'}}(10650)$ using a covariant quark model. We use a molecular-type four-quark current for the coupling of the ${Z}_{b}(10610)$ and ${Z}_{b}^{\ensuremath{'}}(10650)$ to the constituent heavy and light quarks.
Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section
2019
Physics letters / B B793, 188-194 (2019). doi:10.1016/j.physletb.2019.04.038
Corrigendum to “Transverse extension of partons in the proton probed in the sea-quark range by measuring the DVCS cross section” [Phys. Lett. B 793 (…
2019
Physics letters / B B 800, 135129 (2020). doi:10.1016/j.physletb.2019.135129
Measurement of the cross section for hard exclusive π0 muoproduction on the proton
2020
Physics letters / B B805, 135454 (2020). doi:10.1016/j.physletb.2020.135454
Radiative decays of double heavy baryons in a relativistic constituent three-quark model including hyperfine mixing
2010
We study flavor-conserving radiative decays of double heavy baryons using a manifestly Lorentz covariant constituent three-quark model. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit. We discuss in some detail hyperfine mixing effects.
New analysis of ηπ tensor resonances measured at the COMPASS experiment
2018
We present a new amplitude analysis of the $\eta\pi$ $D$-wave in $\pi^- p\to \eta\pi^- p$ measured by COMPASS. Employing an analytical model based on the principles of the relativistic $S$-matrix, we find two resonances that can be identified with the $a_2(1320)$ and the excited $a_2^\prime(1700)$, and perform a comprehensive analysis of their pole positions. For the mass and width of the $a_2$ we find $M=(1307 \pm 1 \pm 6)$~MeV and $\Gamma=(112 \pm 1 \pm 8)$~MeV, and for the excited state $a_2^\prime$ we obtain $M=(1720 \pm 10 \pm 60)$~MeV and $\Gamma=(280\pm 10 \pm 70)$~MeV, respectively.
One-photon transitions between heavy baryons in a relativistic three-quark model
1998
We study one-photon transitions between heavy baryon states in the framework of a relativistic three-quark model. We calculate the one-photon transition rates for ground-state to ground-state transitions and for some specific excited state to ground-state transitions. Our rate predictions for the most important transitions are: $\Gamma(\Sigma^{+}_{c}\to \Lambda_c^+\gamma)= 60.7\pm 1.5 $ KeV, $\Gamma(\Xi^{'+}_{c}\to \Xi_c^+\gamma) = 12.7\pm 1.5$ KeV, $\Gamma(\Lambda_{c1}(2593)\to\Lambda_c^+\gamma)=104.3\pm 1.3$ KeV.
Analyzing lepton flavor universality in the decays Λb→Λc(*)(12±,32−)+ℓν¯ℓ
2018
Lepton flavor universality can be tested in the semileptonic decays Λb→Λc(*), where Λc(*) denotes either the ground state Λc(2286) (with JP=1/2+) or its orbital excitations Λc(2595) (with JP=1/2−) and Λc(2625) (with JP=3/2−). We calculate the differential decay rates as well as the branching fractions of these decays for both tauonic and muonic modes with form factors obtained from a covariant confined quark model previously developed by us. We present results for the rate ratios of the tauonic and muonic modes which provide important tests of lepton flavor universality in forthcoming experiments.
Semileptonic decays of double heavy baryons
2001
We study the semileptonic decays of the lowest lying double heavy baryons using the relativistic three-quark model. We do not employ a heavy quark mass expansion but keep the masses of the heavy quarks and baryons finite. We calculate all relevant form factors and decay rates.
Polarization effects in the cascade decayΛb→Λ(→pπ−)+J/ψ(→ℓ+ℓ−)in the covariant confined quark model
2013
We calculate the invariant and helicity amplitudes for the nonleptonic decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)$ in the covariant confined quark model. We discuss joint angular decay distributions in the cascade decay ${\ensuremath{\Lambda}}_{b}\ensuremath{\rightarrow}\ensuremath{\Lambda}(\ensuremath{\rightarrow}p{\ensuremath{\pi}}^{\ensuremath{-}})+J/\ensuremath{\psi}$, $\ensuremath{\psi}(2S)(\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}})$ and calculate some of the asymmetry parameters that characterize the joint angular decay distribution. We confirm expectations from th…
Theoretical description of the decays Λb→Λ(*)(12±,32±)+J/ψ
2017
We calculate the invariant and helicity amplitudes for the transitions ${\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}^{(*)}({J}^{P})+J/\ensuremath{\psi}$, where the ${\mathrm{\ensuremath{\Lambda}}}^{(*)}({J}^{P})$ are $\mathrm{\ensuremath{\Lambda}}(sud)$-type ground and excited states with ${J}^{P}$ quantum numbers ${J}^{P}={\frac{1}{2}}^{\ifmmode\pm\else\textpm\fi{}}$, ${\frac{3}{2}}^{\ifmmode\pm\else\textpm\fi{}}$. The calculations are performed in the framework of a covariant confined quark model previously developed by us. We find that the values of the helicity amplitudes for the ${\mathrm{\ensuremath{\Lambda}}}^{*}(1520,{\frac{3}{2}}^{\ensu…
Semileptonic decays of the lightJP=1/2+ground state baryon octet
2008
We calculate the semileptonic baryon octet-octet transition form factors using a manifestly Lorentz covariant quark model approach based on the factorization of the contribution of valence quarks and chiral effects. We perform a detailed analysis of SU(3)-breaking corrections to the hyperon semileptonic decay form factors. We present complete results on decay rates and asymmetry parameters including lepton mass effects for the rates.
Covariant ChPT calculation of the hyperon forward spin polarizability
2015
We predict the values for baryon forward spin polarizabilities in fully covariant ChPT and including the virtual contributions of the spin-3/2 states. As the nucleon results are in good agreement with the experimental data and they do not depend on renormalization schemes, we extend the calculations to the hyperon sector.
Light baryons and their electromagnetic interactions in the covariant constituent quark model
2012
We extend the confined covariant constituent quark model that was previously developed by us for mesons to the baryon sector. In our numerical calculation we use the same values for the constituent quark masses and the infrared cutoff as have been previously used in the meson sector. In a first application we describe the static properties of the proton and neutron, and the $\Lambda$-hyperon (magnetic moments and charge radii) and the behavior of the nucleon form factors at low momentum transfers. We discuss in some detail the conservation of gauge invariance of the electromagnetic transition matrix elements in the presence of a nonlocal coupling of the baryons to the three constituent quar…
Semileptonic decays of double heavy baryons in a relativistic constituent three-quark model
2009
We study the semileptonic decays of double heavy baryons using a manifestly Lorentz covariant constituent three-quark model. We present complete results on transition form factors between double-heavy baryons for finite values of the heavy quark/baryon masses and in the heavy quark symmetry limit which is valid at and close to zero recoil. Decay rates are calculated and compared to each other in the full theory, keeping masses finite, and also in the heavy quark limit.
Rare CP-violated η and η′ meson decays and neutron EDM.
2018
The data for the upper limit on the electric dipole moment of the neutron (nEDM) can be explained by using different mechanisms beyond the Standard Model (SM). The nEDM can be generated by a CP-violating transition of η and η′ mesons into pion pairs. We derive the upper limits for the rates of the CP-violating decays η(η′) → 2π are by orders of magnitude more stringent than those from existing experiments so far.
Hyperon forward spin polarizability gamma0 in baryon chiral perturbation theory
2015
We present the calculation of the hyperon forward spin polarizability gamma0 using manifestly Lorentz covariant baryon chiral perturbation theory including the intermediate contribution of the spin 3/2 states. As at the considered order the extraction of gamma0 is a pure prediction of chiral perturbation theory, the obtained values are a good test for this theory. After including explicitly the decuplet states, our SU(2) results have a very good agreement with the experimental data and we extend our framework to SU(3) to give predictions to the hyperons' gamma0 values. Prominent are the Sigma^- and Xi^- baryons as their photon transition to the decuplet is forbidden in SU(3) symmetry and th…
Strong and Radiative Decays of Heavy Flavored Baryons
1999
We analyze strong one-pion and radiative one-photon decays of heavy flavored baryons within a relativistic three-quark model. Employing the same parameters as were used for the description of the semileptonic decays of heavy baryons, we calculate the couplings of one-pion and one-photon transitions of both ground and excited heavy baryon states. We predict the decay rates for all relevant decay modes and compare them with experimental data when available and with the results of other model calculations.
Λb and Λc baryon decays at finite values of heavy quark masses
2000
Semileptonic decays of Lambda_b and Lambda_c baryons are studied within the Relativistic Three-Quark Model using finite heavy quark mass values. Employing the same parameters as have been used previously for the description of exclusive decays of heavy baryons in the heavy quark limit we calculate the six form factors of the process and the corresponding decay rates. Our calculation shows that the ``finite mass'' corrections are important in heavy-to-light transitions and are not negligible in heavy-to-heavy transitions.
Bounds on rare decays of η and η′ mesons from the neutron EDM
2019
We provide model-independent bounds on the rates of rare decays $\ensuremath{\eta}({\ensuremath{\eta}}^{\ensuremath{'}})\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ based on experimental limits on the neutron electric dipole moment (nEDM). Starting from phenomenological $\ensuremath{\eta}({\ensuremath{\eta}}^{\ensuremath{'}})\ensuremath{\pi}\ensuremath{\pi}$ couplings, the nEDM arises at the two-loop level. The leading-order relativistic chiral perturbation theory calculation with the minimal photon coupling to charged pions and a proton inside the loops leads to a finite, counterterm-free result. This is an improvement upon previous estimates which used approximations in evalu…
Form-factor-independent test of lepton universality in semileptonic heavy meson and baryon decays
2021
In the semileptonic decays of heavy mesons and baryons the lepton-mass dependence factors out in the quadratic $\cos^2\theta$ coefficient of the differential $\cos\theta$ distribution. We call the corresponding normalized coefficient the convexity parameter. This observation opens the path to a test of lepton universality in semileptonic heavy meson and baryon decays that is independent of form-factor effects. By projecting out the quadratic rate coefficient, dividing out the lepton-mass-dependent factor and restricting the phase space integration to the $\tau$ lepton phase space, one can define optimized partial rates which, in the Standard Model, are the same for all three $(e,\mu,\tau)$ …