In this paper we investigate the strong decays of the two newly observed bottom-strange mesons $B_{s1}(5830)$ and $B_{s2}^*(5840)$ in the framework of the quark pair creation model. The two-body strong decay widths of $B_{s1}(5830)^0\to B^{*+}K^-$ and $B_{s2}^*(5840)^0\to B^+K^-, B^{*+}K^-$ are calculated by considering $B_{s1}(5830)$ to be a mixture between $|^1P_1>$ and $|^3P_1>$ states, and $B_{s2}^*(5840)$ to be a $|^3P_2>$ state. The double pion decay of $B_{s1}(5830)$ and $B_{s2}^*(5840)$ is supposed to occur via the intermediate state $σ$ and $f_0(980)$. Although the double pion decay widths of $B_{s1}(5830)$ and $B_{s2}^*(5840)$ are smaller than the two-body strong decay widths of $B_{s1}(5830)$ and $B_{s2}^*(5840)$, one suggests future experiments to search the double pion decays of $B_{s1}(5830)$ and $B_{s2}^*(5840)$ due to their sizable decay widths.
The temperature behaviour of the pion width in the hadronic phase is investigated in the framework of the NJL model. The contribution to the width from the pion-pion collision is considered with a scalar sigma-meson as an intermediate state. It is shown that the pion width significantly broadens at $T>0.1$ GeV. Using the two-step iteration method, suggested by Kadanoff and Baym, the pion spectral function in a hot pion gas is calculated at different temperatures.
We estimate pionic decay widths of the narrow charm-strange resonances $D_{sj}(2317)$ and $D_{sj}(2460)$ using the $^3P_0$ model. Their one-pion decays occur through $η$-$π^0$ mixing while the two-pion decays of $D_{sj}(2460)$ occur through the virtual $f_0(980)$ meson. The mixing between $^3P_1$ and $^1P_1$ states enhances the single pion decay width of $D_{sj}(2460)$ and suppresses its double pion decay width significantly. The two-pion decay width of $D_{sj}(2460)$ is much smaller than its one-pion decay width. As a byproduct, we also calculate pionic decay widths of $B_{sj}(5765)$, $B_{sj}…
We study the behavior of the $π^0$ width as a function of temperature and density. We provide simple expressions for the neutral pion width in a hot and dense medium based on a renormalized version of the microscopic Nambu Jona Lasinio model. Then we consider the two cases where the pion mass is finite or vanishes at the critical temperature and discuss the phenomenological consequences of both cases.
The pseudoscalar-vector-vector correlator is constructed using two meson multiplets in the vector and two in the pseudoscalar channel. The parameters are constrained by the operator product expansion at leading order where two or all three momenta are considered as large. Demanding in addition the Brodsky-Lepage limit one obtains (in the chiral limit) a pion-vector-vector correlator with only one free parameter. The singly virtual pion transition form factor and the decay width of omega to pion and photon are independent of this parameter and can serve as cross-checks of the results. The free …
We calculate low-energy meson decay processes and pion-pion scattering lengths in a two-flavour linear sigma model with global chiral symmetry, exploring the scenario in which the scalar mesons $f_0$(600) and $a_0$(980) are assumed to be $\bar q q$ states.
We study the effect of the thermal width of $π$ on the spectral function of $σ$. In order to take into account a finite thermal width of $π$, we replace the internal pion mass in the self-energy of $σ$ with that of the complex pole found in a previous paper. The obtained spectral function for $T\aplg 100 {\rm MeV}$ turns out to possess two broad peaks. Although a sharp peak at $σ\toππ$ threshold was observed in the one-loop calculation without the pion thermal width, the peak is shown to be smeared out. We also search for the poles of the $σ$ propagator and analyze the behavior of the spectral…
We consider the first pion excitation as a sub-continuum resonance in the pseudoscalar channel, and we obtain parameters characterizing this resonance through a global fit of the Borel-parameter dependence of the field-theoretical pseudoscalar Laplace sum rule to its hadronic (pion + pion-excitation + QCD-continuum) content. Our analysis incorporates finite-width deviations from the narrow resonance approximation, instanton effects, and higher-loop perturbative contributions to the pseudoscalar correlator. We obtain the following values (uncertainties reflect 90% confidence levels): mass $M_Π=…
We study the effect of thermal width of $π$ on the spectral function of $σ$ applying a resummation technique called optimized perturbation theory at finite temperature ($T$) to ${\cal O}(4)$ linear sigma model. In order to take into account finite thermal width of $π$, we replace the internal pion mass in the self-energy of $σ$ with that of complex pole found in a previous paper. The obtained spectral function for $T\aplg 100 {\rm MeV}$ turns out to possess two broad peaks. Although a sharp peak at $σ\toππ$ threshold was observed in the one-loop calculation without pion thermal width, the peak…
The electromagnetic pion form factor, $F_π(q^2)$, is calculated for spacelike-$q^2$ in impulse approximation using a confining quark propagator, $S$, and a dressed quark-photon vertex, $Γ_μ$, obtained from realistic, nonperturbative Dyson-Schwinger equation studies. Good agreement with the available data is obtained for $F_π(q^2)$ and other pion observables, including the decay $π^0 \rightarrow γ\,γ$. This calculation suggests that soft, nonperturbative contributions dominate $F_π(q^2)$ at presently accessible~$q^2$.
Investigations of the mass and decays of the exotic hybrid are reviewed, including calculation of the pion1 to eta pion, eta-prime pion decay widths within the QCD sum rules technique. In this calculation, the recently-proposed eta, eta-prime quark mixing scheme is employed. The results indicate that the decay width Gamma(pion1 to eta pion) around 250 MeV is large compared with the decay width Gamma(pion1 to eta-prime pion) around 20 MeV. Inspired by these results, some phenomenological approaches are suggested to gain an understanding of the underlying mechanism of eta pion and eta-prime pion…
Two-parton correlations in the pion are investigated in terms of double parton distribution functions. A Poincaré covariant Light-Front framework has been adopted. As non perturbative input, the pion wave function obtained within the so-called soft-wall AdS/QCD model has been used. Results show how novel dynamical information on the structure of the pion, not accessible through one-body parton distribution, are encoded in double parton distribution functions.
We calculate the width of the delta resonance at leading two-loop order in baryon chiral perturbation theory. This gives a correlation between the leading pion-nucleon-delta and pion-delta couplings, which is relevant for the analysis of pion-nucleon scattering and other processes.
Within a field theoretical model where all damping width effects are treated self-consistently we study the changes of the spectral properties of rho-mesons due to the finite damping width of the pions in dense hadronic matter at finite temperature. The corresponding effects in the di-lepton yields are presented. Some problems concerning the self consistent treatment of vector or gauge bosons are discussed.
The couplings and decay widths of the proceses (1^+,2^+)->(0^-,1^-)+rho are studied with ligh-cone QCD sum rules in the leading order of heavy quark effective theory. These processes are employed to estimate the two pion transition widths of the (1^+,2^+) doublet through the low mass tail of the rho resonance. Our calculation shows that the two pion decay widths are much smaller than the single pion decay widths. However, B_1 and B_2^* mesons should also have significant two pion decay widths around 1.5 MeV.
The widths for $ππ$ decay of the L=1 charm mesons are calculated by describing the pion coupling to light constituents quarks by the lowest order chiral interaction. The wavefunctions of the charm mesons are obtained as solutions to the covariant Blankenbecler-Sugar equation. These solutions correspond to an interaction Hamiltonian modeled as the sum of a linear scalar confining and a screened one-gluon exchange (OGE) interaction. This interaction induces a two-quark contribution to the amplitude for two-pion decay, which is found to interfere destructively with the single quark amplitude. For…
We study the non-forward matrix elements of twist-2 QCD light-ray operators and their representations in terms of skewed and double distributions, considering the pion as well as the nucleon. We point out the importance of explicitly including all twist-2 structures in the double distribution representation, which naturally leads to a ``two-component'' structure of the skewed distribution, with different contributions in the regions |X| > xi/2 and |X| < ξ/2. We compute the skewed and double quark distributions in the pion at a low normalization point in the effective chiral theory based on the…
Two-parton correlations in the pion, a non perturbative information encoded in double parton distribution functions, are investigated in the Nambu and Jona-Lasinio model. It is found that double parton distribution functions expose novel dynamical information on the structure of the pion, not accessible through one-body parton distributions, as it happens in several estimates for the proton target and in a previous evaluation for the pion, in a light-cone framework. Expressions and predictions are given for double parton distributions corresponding to leading-twist Dirac operators in the quark…
The influence of the finite width of $ρ$ meson on the pion momentum distribution is studied quantitatively in the framework of the S-matrix approach combined with a blast-wave model to describe particle emissions from an expanding fireball. We find that the proper treatment of resonances which accounts for their production dynamics encoded in data for partial wave scattering amplitudes can substantially modify spectra of daughter particles originating in their two body decays. In particular, it results in an enhancement of the low-$p_T$ pions from the decays of $ρ$ mesons which improves the qu…
Different aspects of the Gribov--Glauber approach for calculation of inclusive pion double charge exchange (DCX) on nuclei are investigated. Recently we have shown that inelastic rescatterings (IR) with two (and more) pions in the intermediate states give an important contribution to the process of DCX at energies above $\sim0.6 GeV$. In this paper we use the one pion exchange model to study in details amplitudes of two pion production. This allows us to verify theoretical assumptions made in the previous paper and to predict cross section for the forward inclusive pion DCX at energies $\ga1 G…
We examine the pion realization of the short ranged supersymmetric (SUSY) mechanism of neutrinoless double beta decay. It originates from the R-parity violating quark-lepton interactions of the SUSY extensions of the standard model of the electroweak interactions. We argue that pions are dominant SUSY mediators in neutrinoless double beta decay. The corresponding nuclear matrix elements for various isotopes are calculated within the proton-neutron renormalized quasiparticle random phase approximation. We define those isotopes which are most sensitive to the SUSY signal and outlook the present …
In the real-time thermal field theory, the standard expression of shear viscosity for the nucleonic constituents is derived from the two point function of nucleonic viscous stress tensors at finite temperature and density. The finite thermal width or Landau damping is traditionally included in the nucleon propagators. This thermal width is calculated from the in-medium self-energy of nucleon for different possible pion-baryon loops. The dynamical part of nucleon-pion-baryon interactions are taken care by the effective Lagrangian densities of standard hadronic model. The shear viscosity to entr…
The pionic decay rates of the excited $L=0,1$ $D$ mesons are calculated with a Hamiltonian model within the framework of the covariant Blankenbecler-Sugar {equation.} The interaction between the light quark and charm antiquark is described by a linear scalar confining and a screened one-gluon exchange interaction. The decay widths of the $D^*$ mesons obtain a contribution from the exchange current that is associated with the linear scalar confining interaction. If this contribution is taken into account along with the single quark approximation, the calculated decay rates of the charged $D^*$ …
We study the influence of the finite damping width of pions on the in-medium properties of the rho-meson in an interacting meson gas model at finite temperature. Using vector dominance also implications on the resulting dilepton spectra from the decay of the rho-meson are presented. A set of coupled Dyson equations with self energies up to the sunset diagram level is solved self consistently. Following a Phi-derivable scheme the self energies are dynamically determined by the self consistent propagators. Some problems concerning the self consistent treatment of vector or gauge bosons on the pr…
Decay of light quark excited baryons in the double pion channel is discussed, as a particular way of investigating poorly know baryon resonances and searching for "missing states" predicted by quark models. A possible approach to the data analysis is discussed and some preliminary data from the CLAS collaboration at Jefferson Laboratory are presented.
In the present work, we investigate the production of $P_{c}$ and $Z_c(3900)/Z_{cs}(3985)$ states in the processes of $πp \rightarrow Z_{c}(3900) P_{c} $/$Kp\rightarrow Z_{cs}(3985) P_{c}$ with an effective Lagrangian approach. Our estimations indicates that the cross sections depends on the model parameters and beam energies, in particular, the cross sections for $πp \to Z_c(3900) P_c(4312)$ and $πp \to Z_c(3900) P_c(4440)$ are similar and can reach up to 10 nb, while those for $πp \to Z_c(3900) P_c(4457)$ can be 30 nb. As for $Kp \to Z_{cs}(3985)P_c$, the cross sections are about 2.5 times s…
We calculate the width of the Roper resonance at next-to-leading order in a systematic expansion of baryon chiral perturbation theory with pions, nucleons, and the delta and Roper resonances as dynamical degrees of freedom. Three unknown low-energy constants contribute up to the given order. One of them can be fixed by reproducing the empirical value for the width of the Roper decay into a pion and a nucleon. Assuming that the remaining two couplings of the Roper interaction take values equal to those of the nucleon, the result for the width of the Roper decaying into a nucleon and two pions i…
In this work, we investigate the decay widths and the line shapes of the open-charm radiative and pionic decays of Y(4274) with the $D_s\bar{D}_{s0}(2317)$ molecular charmonium assignment. Our calculation indicates that the decay widths of $Y(4274)\to D^{+}_{s}D^{*-}_{s}γ$ and $Y(4274)\to D^+_{s}D^-_{s}π^0$ can reach up to 0.05 keV and 0.75 keV, respectively. In addition, the result of the line shape of the photon spectrum of $Y(4274)\to D_s^+ {D}_s^{*-} γ$ shows that there exists a very sharp peak near the large end point of photon energy. The line shape of the pion spectrum of $Y(4274)\to D_…
At the quark level there are basically two types of contributions of R-parity violating SUSY (RPV SUSY) to neutrinoless double beta decay: the short-range contribution involving only heavy virtual superpartners and the long-range one with the virtual squark and neutrino. Hadronization of the effective operators, corresponding to these two types of contributions, may in general involve virtual pions in addition to the close on-mass-shell nucleons. It is known that the short-range contribution is dominated by the pion exchange. In the present paper we show that this is also true for the long-ran…
Recent results from phenomenological studies of the CLAS data on 2$π$ electroproduction off proton are presented. The analysis is focused on extracting of N $\to$ $N^{*}$ electromagnetic transition amplitudes from the full data set on unpolarized 1-differential 2$π$ cross-sections.
We perform a lattice study of double parton distributions in the pion, using the relationship between their Mellin moments and pion matrix elements of two local currents. A good statistical signal is obtained for almost all relevant Wick contractions. We investigate correlations in the spatial distribution of two partons in the pion, as well as correlations involving the parton polarisation. The patterns we observe depend significantly on the quark mass. We investigate the assumption that double parton distributions approximately factorise into a convolution of single parton distributions.
We show that the transverse momentum dependent transversity function is proportional to the longitudinal polarization of a quark in a transversely polarized proton. This result suggests an alternative, convenient method for determining transversity, without knowing unusual fragmentation functions. The method consists of measuring the double spin azimuthal asymmetry in semi-inclusive pion leptoproduction by a transversely polarized proton target. The asymmetry, which is twist 3, is estimated to be more than 10% under the most favorable conditions. The experiment we suggest is feasible at facili…
We consider the cos(phi) dependence of the longitudinal double-spin asymmetry for charged pion electroproduction in semi-inclusive deep inelastic scattering, emphasizing intrinsic transverse momentum effects. This azimuthal asymmetry allows to measure the cos(phi) moments of the unpolarized and double-spin cross-section, simultaneously. The size of the asymmetry, in the approximation where all twist-3 interaction-dependent distribution and fragmentation functions are set to zero, is estimated for HERMES kinematics; both the spin-independent and the double-spin cos(phi) moments are predicted to…
We enforce chiral Ward identities on the vertices of the linear sigma model to take into account the width of the scalar sigma, considered as a true physical resonance. We consider pion scattering at very low energies and, from a fit to the measured phase shifts in the various angular momentum and isospin channels, conclude a mass for the sigma of 600+200-100 MeV. Its width turns out to be of the same size.
We present a new contribution of the R-parity violating supersymmetry (SUSY) to neutrinoless double beta decay via the pion exchange between decaying neutrons. The pion coupling to the final state electrons is induced by the R-parity violating SUSY interactions. We have found this pion-exchange mechanism to dominate over the conventional two-nucleon one. The latter corresponds to direct interaction between quarks from two decaying neutrons without any light hadronic mediator like pion. The constraints on the certain R-parity violating SUSY parameters are extracted from the current experimental…
Neutral and charged pion Form Factors in the intermediate-energy region from double-dilaton HQCD model
Universitat Autònoma de Barcelona（巴塞罗那自治大学）；Institut de Física d’Altes Energies (IFAE)（高能物理研究所）；The Barcelona Institute of Science and Technology (BIST)（巴塞罗那科学与技术研究院）
We consider a globally invariant chiral Lagrangian that contains vector and axial-vector mesons. We compute the f0(600) decay width into two pions and pion-pion scattering lengths and compare with the corresponding results in which the (axial-)vector degrees of freedom decouple. We show that the role of vector mesons has a great impact on these quantities.
Within a dynamical coupled-channels model which has already been fixed from analyzing the data of the pi N -> pi N and gamma N -> pi N reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, W< 1.7 GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects due to the direct gamma N -> pi pi N mechanism, the interplay between the resonant and non-resonant amplitudes, and the coupled-channels effects. The model parameters…
We consider two simple covariant models for pions (one with scalar and the other with spin-1/2 constituents). Pion generalized parton distributions are derived by integration over the light-cone energy. The model distributions are consistent with all known properties of generalized parton distributions, including positivity. We also construct the corresponding double distributions by appealing to Lorentz invariance. These ostensibly constructed double distributions lead to different generalized parton distributions that need not respect the positivity constraints. This inconsistency arises fro…
Owing to the Kubo relation, the shear viscosities of pionic and nucleonic components have been evaluated from their corresponding retarded correlators of viscous stress tensor in the static limit, which become non-divergent only for the non-zero thermal widths of the constituent particles. In the real-time thermal field theory, the pion and nucleon thermal widths have respectively been obtained from the pion self-energy for different meson, baryon loops and the nucleon self-energy for different pion-baryon loops. We have found a non-monotonic momentum distributions of pion and nucleon thermal …
Key Laboratory of Atomic and Subatomic Structure and Quantum Control (MOE), Guangdong-Hong Kong Joint Laboratory of Quantum Matter（原子与亚原子结构及量子控制重点实验室（教育部），粤港澳量子物质联合实验室）；State Key Laboratory of Nuclear Physics and Technology, Institute of Quantum Matter, South China Normal University（核物理与技术国家重点实验室，华南师范大学量子物质研究所）；Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Nuclear Science（广东省物质结构与基本相互作用卓越研究中心，广东省核科学重点实验室）；Southern Center for Nuclear-Science Theory (SCNT), Institute of Modern Physics, Chinese Academy of Sciences（南方核科学理论中心（SCNT），中国科学院近代物理研究所）；Research Center for Nuclear Physics (RCNP), Osaka University（大阪大学核物理研究中心（RCNP））；Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Institute of Modern Physics, Fudan University（核物理与离子束应用重点实验室（教育部），复旦大学近代物理研究所）；Shanghai Research Center for Theoretical Nuclear Physics, NSFC and Fudan University（上海理论核物理研究中心，国家自然科学基金委员会与复旦大学）
We show that the semi-leptonic decay B+ -> pi+ pi- l+ ν_l can be used as a source of information for two-pion distribution amplitudes. The connection between these amplitudes and the B-meson decay width is achieved by the light cone sum rule method. We show the relevant distribution amplitudes and give the formula for the decay width.
Data on single- and double-charged pion electroproduction off protons are successfully described in the second and third nucleon resonance regions with common N* photocouplings. The analysis was carried out using separate isobar models for both reactions. From the combined analysis of two exclusive channels, the gamma* p --> N*+ helicity amplitudes are obtained for the resonances P11(1440), D13(1520), S31(1620), S11(1650), F15(1680), D33(1700), D13(1700), and P13(1720) at Q2=0.65 GeV/c^2.
Within the resonance chiral effective theory we study the dressed propagators of the spin-1 fields, as arise from a Dyson-Schwinger resummation perturbatively constructed from loop diagrams with absorptive contributions in the s-channel. We apply the procedure to the vector pion form factor and the elastic pion-pion scattering to obtain the off-shell width of the rho_0 meson. We adopt a definition of the off-shell width of spin-1 meson resonances that satisfies the requirements of analyticity, unitarity, chiral symmetry and asymptotic behaviour ruled by QCD. To fulfil these constraints the res…
We examine the pion exchange mode of neutrinoless double beta decay induced by the R-parity violating quark-lepton operators of the supersymmetric (SUSY) extensions of the standard model of the electroweak interactions. The corresponding nuclear matrix elements are evaluated within the renormalized quasiparticle random phase approximation with proton-neutron pairing, which includes the Pauli effect of fermion pairs and does not collapse for a physical value of the nuclear force strength. It is argued that the pion-exchange mode of neutrinoless double beta decay dominates over the conventional …
The role of the nucleon resonances in the double polarization observables of pion photoproduction is investigated by using the resonance parameters predicted by Capstick and Roberts. As an example, we show that the not-well-determined two-star resonance N$^{-}_{3/2}$(1960) can be examined by performing experiments on beam-recoil polarization at large angles.
First comprehensive data on the evolution of nucleon resonance photocouplings with photon virtuality Q^2 are presented for excited proton states in the mass range from 1.4 to 2.0 GeV. N^* photocouplings were determined in phenomenological analysis of CLAS data on 2 pi photo and electroproduction within the framework of the JLAB-MSU phenomenological model.
The contribution of the rho^{\pm} vector meson to the tau -> pi pi nu gamma decay is considered as a potential source for the determination of the magnetic dipole moment of this light vector meson. In order to keep gauge-invariance of the whole decay amplitude, a procedure similar to the fermion loop-scheme for charged gauge bosons is implemented to incorporate the finite width effects of the rho^{\pm} vector meson. The absorptive pieces of the one-loop corrections to the propagators and electromagnetic vertices of the rho^{\pm} meson and W^{\pm} gauge boson have identical forms in the limit o…
We consider within a generalized QCD factorization approach, the high energy inclusive polarized process p p --> pion + X, including all intrinsic partonic motions. Several new spin and k_T-dependent soft functions appear and contribute to cross sections and spin asymmetries. We present here formal expressions for transverse single spin asymmetries and double longitudinal ones. The transverse single spin asymmetry, A_N, is considered in detail, and all contributions are evaluated numerically. It is shown that the azimuthal phase integrations strongly suppress most contributions, leaving at wor…
The pionic decay of a possible d'-dibaryon in the process d' --> pi + N + N is studied in the microscopic quark shell model and with a single-quark transition operator describing the transition q --> pi + q'. For the d' with quantum numbers J^P=0^-, T=0, we employ a six-quark shell-model wave function with a spatial s^5p [51]_X-configuration with N=1 harmonic oscillator quanta. It is shown that the pionic decay width depends strongly on the mass and size of the d'. In the case that the calculated d' mass is close to the experimental one a small pionic decay width of 0.04 MeV is obtained. This …
In order to reveal possible mass shifts of the vector mesons in a dense strongly interacting medium presumably created in high energy heavy ion collisions it is necessary to know their free masses reliably. The rho(770) mass quoted in the last two editions of the Review of Particle Physics is significantly larger than the values quoted in previous editions. The new value is mostly influenced by the results of recent experiments CMD-2 and SND at the VEPP-2M e+e- collider at Novosibirsk. We show that the values of the mass and width of the rho(770) meson measured in the e+e- -> pi+pi- annihilati…
The forward inclusive pion double charge exchange reaction, ^{16}O(pi^-,pi^+)X, at T_0 = 0.50 and 0.75 GeV has been studied in the kinematical region where an additional pion production is forbidden by energy-momentum conservation. The experiment was performed with the SKS spectrometer at KEK PS. The measured ratio of double charge exchange cross-section for these energies dsigma(0.50 GeV)/dOmega / dsigma(0.75 GeV)/dOmega = 1.7 +/- 0.2, disagrees with the value of 7.2 predicted within the conventional sequential single charge exchange mechanism. Possible reasons for the disagreement are discus…
In this article, we study the two-pion decays in the $P$-wave to $S$-wave charmonium transitions with the heavy meson effective theory, and make qualitative predictions for the ratios among the two-pion decay widths.
In this work we study the implications of light-quark pionic matter at finite temperatures on the properties of open and hidden charm mesons. The meson-meson interactions are described by means of a chiral unitary approach accounting for coupled channels effects. The in-medium Lippmann-Schwinger Equations, which consider the change in self-energy that the mesons acquire from interacting with the surrounding pionic matter, are solved self-consistently, and the spectral functions of the mesons in the hot pion bath are obtained. It is observed that the charmed mesons develop a quite substantial p…
We estimate the contributions by double-parton interactions to the cross sections for pp->pi^0 pi^0 X and dA->pi^0 pi^0 X at RHIC. We find that such contributions become important at large forward rapidities of the produced pions. This is in particular the case for dA scattering, where they strongly enhance the azimuthal-angular independent "pedestal" component of the cross section, providing a natural explanation of this feature of the RHIC dA data. We argue that the discussed processes open a window to studies of double quark distributions in nucleons. We also briefly address the roles of sh…
The widths for pionic decays of lowest two excited doublets (0^+,1^+) and (1^+,2^+) of heavy mesons are studied with QCD sum rules in the leading order of heavy quark effective theory. The ambiguity due to presence of two distinct 1^+ states are solved. The soft pion approximation is not used.
The latest measurements of the atomic level width in Sigma-hyperonic Pb atom offer the most accurate datum in the region of low-energy Sigma-hyperon physics. Atomic widths are due to the conversion of Sigma-nucleon into Lambda-nucleon. In high angular momentum states this conversion is dominated by the one-pion exchange. A joint analysis of the data of the scattering of negative-Sigma on proton converting into a Lambda and a neutron and of the atomic widths allows to extract a pseudovector pion-hyperon-Sigma coupling constant of 0.048 with a statistical error of +-0.005 and a systematic one of…
We analyze the experimental data on the inclusive double differential cross section by neutrinos charged current, measured by T2K, with the same model which was successful for the MiniBooNE quasielastic cross sections. As in our previous analysis the multinucleon component is needed in order to reproduce the data. For the total cross section our evaluation is smaller than the SciBooNE data above 1 GeV. This indicates the opening of a new channel not included in our evaluation, presumably the two pion emission channel. We also check that our description holds for the exclusive single pion produ…
