Forward-backward (charge) asymmetry in the processes of $e^+e^-$ annihilation into a pair of charged pseudoscalar mesons is recalculated in the one-loop approximation. The exact dependence on the meson masses is taken into account. Results known in the literature are partially corrected. The bulk of the charge asymmetry appears due to double-photon exchange in $s$ channel. Experimental studies of the asymmetry can be used to verify the point-like approximation used in calculation of radiative corrections due to emission of photons by pions or kaons.
We revisit the global QCD analysis of parton-to-kaon fragmentation functions at next-to-leading order accuracy using the latest experimental information on single-inclusive kaon production in electron-positron annihilation, lepton-nucleon deep-inelastic scattering, and proton-proton collisions. An excellent description of all data sets is achieved, and the remaining uncertainties in parton-to-kaon fragmentation functions are estimated and discussed based on the Hessian method. Extensive comparisons to the results from our previous global analysis are made.
We examine effects of final state interactions (FSI) in kaon decays using a new scheme without the Omnes function, and show that while Delta I=1/2 rule is impossible to be explained in terms of FSI alone, $ε'/ε\sim 16.5\times 10^{-4}$ is obtained through FSI, if the calculation is concerned only with the CP-violating parts. The pi-pi contribution to the m_L-m_S mass difference is shown to be about 0.14, if the sizes of the CP conserving amplitudes A_0 and A_2 are correctly given.
We study inelastic meson-meson scattering that is governed by quark-antiquark annihilation and creation involving a quark and an antiquark annihilating into a gluon, and subsequently the gluon creating another quark-antiquark pair. The resultant hadronic reactions include for I=1: pion + pion to rho + rho, kaon + antikaon to kaon* + antikaon*, kaon + antikaon* to kaon* + antikaon*, kaon* + antikaon to kaon* + antikaon*, as well as pion + pion to kaon + antikaon, pion + rho to kaon + antikaon*, pion + rho to kaon* + antikaon, and kaon + antikaon to rho + rho. In each reaction, one or two Feynma…
We evaluate the rare radiative kaon decays K_{L,S} -> 3 gamma. Applying the requirements of gauge invariance and Bose symmetry, we derive a general form of the decay amplitude, including both parity-conserving and parity-violating contributions. We employ a chiral-Lagrangian approach combined with dimensional analysis arguments to estimate the branching ratios of these decays in the standard model, obtaining values as large as B(K_L -> 3 gamma) ~ 1 x 10^{-14} and B(K_S -> 3 gamma) ~ 2 x 10^{-17}, which exceed those found previously by a few orders of magnitude. Measurements on the branching ra…
A completely relativistic quark model in the Bethe-Salpter framework is employed to calculate the exclusive production ratio of the neutral over charged Kaon pair in $e^+e^-$ annihilation continuum region for center of mass energies smaller than the $J/Ψ$ mass. The valence quark charge plays the key rôle. The cancellation of the diagrams for the same charge case (in $K_S + K_L$) and the non-cancellation of the diagrams for the different charge case (in $K^-+K^+$) lead to the ratio as $(m_s-m_d)^2/M_{Kaon}^2 \sim 1/10$.
We present an updated discussion of $K\raπ\bar{l} l$ decays in a combined framework of chiral perturbation theory and Large--$N_c$ QCD, which assumes the dominance of a minimal narrow resonance structure in the invariant mass dependence of the $ \bar{l} l$ pair. The proposed picture reproduces very well, both the experimental $K^+\raπ^+ e^+ e^-$ decay rate and the invariant $e^+ e^-$ mass spectrum. The predicted Br$(K_S\raπ^0 e^+ e^-)$ is, within errors, consistent with the recently reported result from the NA48 collaboration. Predictions for the $K\raπμ^{+}μ^{-}$ modes are also obtained. We f…
We analyse the impact of the recent measurement of kaonic hydrogen X rays by the SIDDHARTA collaboration on the allowed ranges for the kaon-deuteron scattering length in the framework of non-relativistic effective field theory. Based on data from KN scattering only, we predict the kaon-deuteron scattering length A_Kd= (-1.46 + i 1.08) fm, with an estimated uncertainty of about 25% in both the real and the imaginary part.
The anti-kaon nucleon system close to threshold is analyzed in view of the new accurate DEAR kaonic hydrogen data. The calculations are performed using chiral SU(3) effective field theory in combination with non-perturbative schemes based on coupled channels. Several variants of such approaches are compared with experimental data and the differences in the results are discussed. Coulomb and isospin breaking effects turn out to be important and are both taken into account. The pole structure of the Lambda(1405) resonance close to the anti-kaon nucleon threshold is critically examined.
In this work we discuss the interest of measuring the ratio of of $p\bar p$ annihilation into kaon and pion pairs near the threshold region, where $S$ state dominates. It is shown that a good agreement with existing data on the ratio of the yields of charged kaon to pion pairs is obtained taking into account not only quark rearrangement in the incident hadrons, but also vacuum excitations.
We apply the modern multiloop methods to the calculation of the total cross sections of electron-positron annihilation to 2 and 3 photons exactly in $s/m^2$ with the accuracy $O(α^3)$. Examining the asymptotics of our results, we find agreement with Ref. [Andreassi_et_al_1962] and discover mistakes in the results of Refs. [Eidelman&Kuraev_1978,Berends&Kleiss_1981]. This mistake is due to the terms, omitted in differential cross section in Refs. \[Eidelman&Kuraev_1978,Berends&Kleiss_1981], which are peaked in the kinematic region with all three photons being quasi-parallel to the collision axis…
We re-examine the stop co-annihilation scenario of the Minimal Supersymmetric Standard Model, wherein a bino-like lightest supersymmetric particle has a thermal relic density set by co-annihilations with a scalar partner of the top quark in the early universe. We concentrate on the case where only the top partner sector is relevant for the cosmology, and other particles are heavy. We discuss the cosmology with focus on low energy parameters and an emphasis on the implications of the measured Higgs boson mass and its properties. We find that the irreducible direct detection signal correlated wi…
We study the S-wave kaon-nucleon interactions for strangeness S=-1 in a novel relativistic chiral unitary approach based on coupled channels. Dispersion relations are used to perform the necessary resummation of the lowest order relativistic chiral Lagrangian. A good description of the data in the K^- p, πΣand πΛchannels is obtained. We show how this method can be systematically extended to higher orders, emphasizing its applicability to any scenario of strong self-interactions where the perturbative series diverges even at low energies. Discussions about the differences to existing approaches…
We present new functional form of pion and kaon fragmentation functions up to next-to-leading order obtained through a global fit to single-inclusive electron-positron annihilation data and also employ, the semi-inclusive deep inelastic scattering asymmetry data from HERMES and COMPASS to determine fragmentation functions. Also we apply very recently electron-positron annihilation data from BaBar and Belle at $\sqrt{s}=10.54$ GeV and $\sqrt{s}=10.52$ GeV, respectively. In this analysis we consider the impression of semi-inclusive deep inelastic scattering asymmetry data on the fragmentation fu…
The European Organization for Nuclear Research (CERN) has recently approved a world-unique QCD facility in which an updated version of the external M2 beam line of the CERN SPS in conjunction with a universal spectrometer of the COMPASS experiment is used. One of its main goals is to use highly intense and energetic kaon beams to map out the complete spectrum of excited kaons with an unprecedented precision; having a broad impact not only on low-energy QCD phenomenology, but also on many high-energy particle processes where excited kaons appear, such as the study of CP violation in heavy-meson…
Processes of electron-positron annihilation into charged pions and kaons are considered. Radiative corrections are taken into account exactly in the first order and within the leading logarithmic approximation in higher orders. A combined approach for accounting exact calculations and electron structure functions is used. An accuracy of the calculation can be estimated about 0.2%.
Two-body decays of B mesons are studied by decomposing their amplitude into a sum of factorizable and non-factorizable ones. The former is estimated by using the naive factorization while the latter is calculated by using a hard pion (or kaon) approximation in the infinite momentum frame. It is seen that the non-factorizable contribution is small but not negligible in color favored decays while it is more important in color mismatched decays.
We present a detailed assessment of uncertainties in parton-to-pion and parton-to-kaon fragmentation functions obtained in recent global QCD analyses of single-inclusive hadron production data at next-to-leading order accuracy. We use the robust Lagrange multiplier approach for determining uncertainties to validate the applicability of the simpler but approximate Hessian method. Extensive comparisons of the results obtained within both methods are presented for the individual parton-to-pion and kaon fragmentation functions. We provide Hessian eigenvector sets of pion and kaon fragmentation fun…
We report on the handbag contribution to two-photon annihilation into pion and kaon pairs at large energy and momentum transfer. The underlying physics of the mechanism is outlined and characteristic features and predictions are presented.
We revisit the calculation of electroweak bremsstrahlung contributions to dark matter annihilation. Dark matter annihilation to leptons is necessarily accompanied by electroweak radiative corrections, in which a $W$ or $Z$ boson is also radiated. Significantly, while many dark matter models feature a helicity suppressed annihilation rate to fermions, bremsstrahlung process can remove this helicity suppression such that the branching ratios Br($\ell νW $), Br($\ell^+\ell^-Z$), and Br($\barννZ$) dominate over Br($\ell^+\ell^-$) and Br($\barνν$). We find this is most significant in the limit wher…
I reconsider the forward-backward asymmetry for flavoured quarks in electron-positron annihilation. I suggest an infrared-safe definition of this observable, such that the asymmetry may be computed in perturbative QCD with massless quarks. With this definition, the first and second order QCD corrections are computed.
The main aim of this paper is a new determination of transverse momentum dependence of unpolarized fragmentation function (TMD FFs) in single inclusive hadron production in electron-positron annihilation (SIA) process. Motivated by the need for a reliable and consistent determination of TMD FFs, we use the most recent TMD production cross sections of charged pions ($π^\pm$), kaons ($K^\pm$) and protons/antiprotons ($p/\bar{p}$) measured in inclusive $e^+e^-$ collisions by Belle Collaboration. These datasets are the first transverse momentum dependence of identified light charged hadron measure…
We study the e^{+}e^{-} to phi pi pi reaction for pions in an isoscalar s-wave which is dominated by loop mechanisms. For kaon loops we start from the conventional RCHPT, but use the unitarized amplitude for KbarK-pipi scattering and the full kaon form factor instead of the lowest order terms. We study also effects of vector mesons using RCHPT supplemented with the conventional anomalous term for VVP interactions and taking into account the effects of heavy vector mesons in the K*K transition form factor. We find a peak in the dipion invariant mass around the f_{0}(980) as in the experiment. S…
We calculate the non-singlet, the pure singlet contribution, and their interference term, at $O(α^2)$ due to electron-pair initial state radiation to $e^+ e^-$ annihilation into a neutral vector boson in a direct analytic computation without any approximation. The correction is represented in terms of iterated incomplete elliptic integrals. Performing the limit $s \gg m_e^2$ we find discrepancies with the earlier results of Ref.~\cite{Berends:1987ab} and confirm results obtained in Ref.~\cite{Blumlein:2011mi} where the effective method of massive operator matrix elements has been used, which w…
A combined analysis of the electromagnetic pion and kaon form factors in the neighborhood of J/psi and psi(2S) and of the strong decay amplitude of these resonances into kaons is presented. In the presence of a large relative phase between strong and electromagnetic resonance amplitudes the branching ratio, as measured in electron-positron annihilation, receives an additional contribution from the interference between resonance and continuum amplitude neglected in earlier papers. Our study is model independent and does not rely on the SU(3) symmetry assumptions used in earlier papers. We note …
Production of $p\bar{p}$ and $n\bar{n}$ pairs in $e^{+}e^{-}$ annihilation near the threshold of the process is discussed with account for the new experimental data appeared recently. Since a significant part of these new data was obtained at energies noticeably exceeding the threshold, we also take into account the form factor describing the amplitude of $N\bar{N}$ pair production at small distances. The effective optical potential, which describes a sharp dependence of the $N\bar{N}$ production cross sections near the threshold, consists of the central potential for $S$ and $D$ waves and the…
We present new sets of pion and kaon fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either pions or kaons identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions without the need of non trivial flavor symmetry assumptions. The resulting sets are in go…
The inert doublet model, a minimal extension of the Standard Model by a second higgs doublet with no direct couplings to quarks or leptons, is one of the simplest scenarios that can explain the dark matter. In this paper, we study in detail the impact of dark matter annihilation into three-body final state on the phenomenology of the inert doublet model. We find that this new annihilation mode dominates, in a relevant portion of the parameter space, over those into two-body final states considered in previous analysis. As a result, the computation of the relic density is modified and the viabl…
We perform the first iterative Monte Carlo (IMC) analysis of fragmentation functions constrained by all available data from single-inclusive $e^+ e^-$ annihilation into pions and kaons. The IMC method eliminates potential bias in traditional analyses based on single fits introduced by fixing parameters not well contrained by the data and provides a statistically rigorous determination of uncertainties. Our analysis reveals specific features of fragmentation functions using the new IMC methodology and those obtained from previous analyses, especially for light quarks and for strange quark fragm…
The cross section for back-to-back hadron pair production in $e^+e^-$ annihilation provides access to the dihadron fragmentation functions (DiFF) needed to extract nucleon parton distribution functions from the semi-inclusive deep inelastic scattering (SIDIS) experiments with two detected final state hadrons. Particular attention is given to the so-called interference DiFF (IFF), which makes it possible to extract the transversity parton distribution of the nucleon in the collinear framework. However, previously unnoticed discrepancies were recently highlighted between the definitions of the I…
We present new sets of fragmentation functions for charged pions, charged kaons, and protons, both at the leading and next-to-leading orders. They are fitted to the scaled-momentum distributions of these hadrons measured in e+e- annihilation on the Z-boson resonance at CERN LEP1 and SLAC SLC. These data partly come as light-, charm-, bottom-quark-enriched and gluon-jet samples, which allows us to treat all partons independently, after imposing the SU(2) flavour symmetry relations. In order to gain sensitivity to the scaling violation in fragmentation, we also include data from SLAC PEP, with c…
We present new sets of pion, kaon, proton and inclusive charged hadron fragmentation functions obtained in NLO combined analyses of single-inclusive hadron production in electron-positron annihilation, proton-proton collisions, and deep-inelastic lepton-proton scattering with either particles identified in the final state. At variance with all previous fits, the present analyses take into account data where hadrons of different electrical charge are identified, which allow to discriminate quark from anti-quark fragmentation functions.
We present a new determination of unpolarised charged pion and kaon fragmentation functions from a set of single-inclusive electron-positron annihilation and lepton-nucleon semi-inclusive deep-inelastic scattering data. The determination includes next-to-next-to-leading order QCD corrections to both processes, and is carried out in a framework that combines a neural-network parametrisation of fragmentation functions with a Monte Carlo representation of their uncertainties. We discuss the quality of the determination, in particular its dependence on higher order corrections.
The subject of the charged-to-neutral yield ratio for B{\bar B} and D{\bar D}pairs near their respective thresholds in e^+e^- annihilation is revisited. As previously argued for the B mesons, this ratio should exhibit a substantial variation across the Upsilon(4S) resonance due to interference of the resonance scattering phase with the Coulomb interaction between the charged mesons. A simple alternative derivation of the expression describing this effect is presented here, and the analysis is extended to include the D meson production in the region of the psi(3770) resonance. The available dat…
I study the very recently discovered S=-2 resonance Xi--(1886) by the NA49 collaboration at the CERN SPS. This resonance was already predicted, with a mass close to 1.9 GeV, in a recent publication mostly dedicated to the S=1 resonance Theta+(1540). To confirm this recent prediction, I apply the same standard quark model with a quark-antiquark annihilation constrained by chiral symmetry. This method also explained with success the repulsive hard core of nucleon-nucleon, kaon-nucleon exotic scattering, and the short range attraction present in pion-nucleon and pion-pion non-exotic scattering. I…
In this work we study the e^{+}e^{-}\toϕK^{+}K^{-} reaction. The leading order electromagnetic contributions to this process involve the γ*ϕ K^{+}K^{-} vertex function with a highly virtual photon. We calculate this function at low energies using RχPT supplemented with the anomalous term for the VV'P interactions. Tree level contributions involve the kaon form factors and the K*K transition form factors. We improve this result, valid for low photon virtualities, replacing the lowest order terms in the kaon form factors and K*K transition form factors by the form factors as obtained in UχPT in …
We make a detailed analysis of the indirect diffuse gamma-ray signals from dark matter annihilation in the Galaxy. We include the prompt emission, as well as the emission from inverse Compton scattering whenever the annihilation products contain light leptons. We consider both the contribution from the smooth dark matter halo and that from substructures. The main parameters for the latter are the mass function index and the minimal subhalo mass. We use recent results from N-body simulations to set the most reasonable range of parameters, and find that the signal can be boosted by a factor rang…
If neutrinos are a significant contributor to the matter density of the universe, then they should have $\sim$ eV mass and cluster in galactic (super) cluster halos, and possibly in galactic halos as well. It was noted in the early 1980's that cosmic ray neutrinos with energy within $δE/E_R=Γ_Z/M_Z \sim 3%$ of the peak energy $E_R=4 (eV/m_ν)\times 10^{21}$ eV will annihilate on the nonrelativistic relic antineutrinos (and vice versa) to produce the Z-boson with an enhanced, resonant cross section of ${\cal O}(G_F)\sim 10^{-32}{cm}^2$. The result of the resonant neutrino annihilation is a hadro…
Recently, various cross sections of e+e- annihilation into hadrons were accurately measured in the energy range from 0.37 to 1.39 GeV with the CMD-2 detector at the VEPP-2M collider. In the pi+pi- channel a systematic uncertainty of 0.6% has been achieved. A Monte-Carlo Generator Photon Jets (MCGPJ) was developed to simulate events of the Bhabha scattering as well as production of two charged pions, kaons and muons. Based on the formalism of Structure Functions, the leading logarithmic contributions related to the emission of photon jets in the collinear region are incorporated into the MC gen…
Antiproton--proton annihilation into light mesons is revisited in the few GeV energy domain, in view of a global description of the existing data. An effective meson model is developed, with mesonic and baryonic degrees od freedom in $s$, $t$, and $u$ channels. Regge factors are added to reproduce the proper energy behavior and the forward and backward peaked behavior. A comparison with existing data and predictions for angular distributions and energy dependence are done for charged and neutral pion pair production.
Apparent channel-dependent violations of the OZI rule in nucleon-antinucleon annihilation reactions are discussed in the presence of an intrinsic strangeness component in the nucleon. Admixture of strange-antistrange quark pairs in the nucleon wave function enables the direct coupling to the phi-meson in the annihilation channel without violating the OZI rule. Three forms are considered in this work for the strangeness content of the proton wave function, namely, the uud cluster with a strange-antistrange sea quark component, kaon-hyperon clusters based on a simple chiral quark model, and the …
We present new sets of fragmentation functions for charged pions and kaons, both at leading and next-to-leading order. They are fitted to data on inclusive charged-hadron production in $e^+e^-$ annihilation taken by TPC at PEP ($\sqrt s=29$~GeV) and to similar data by ALEPH at LEP, who discriminated between events with charm, bottom, and light- flavour fragmentation in their charged-hadron sample. We treat all partons independently and to properly incorporate the charm and bottom thresholds. Due to the sizeable energy gap between PEP and LEP, we are sensitive to the scaling violation in the fr…
We investigate the soft handbag contribution to two-photon annihilation into pion or kaon pairs at large energy and momentum transfer. The amplitude is expressed as a hard gamma gamma -> q qbar subprocess times a form factor describing the soft transition from q qbar to the meson pair. We find the calculated angular dependence of the cross section in good agreement with data, and extract annihilation form factors of plausible size. A key prediction of the handbag mechanism is that the differential cross section is the same for charged and neutral pion pairs, in striking contrast with what is f…
The recent precision measurement of the relative yield of $D^+D^-$ and $D^0 \bar D^0$ meson pairs at the $ψ(3770)$ peak in $e^+e^-$ annihilation is about 3.7 sigma away from a straightforward theoretical estimate. It is argued that combined with an even more significant deviation of similar ratio for the $B$ mesons at the $Υ(4S)$ peak, this provides an insight into the structure of heavy mesons and requires both a form factor, corresponding to their finite `size', and a strong interaction between the mesons mesons in the isovector state $I^G(J^P) = 1^+(1^-)$. It is also argued that the data fo…
Fragmentation functions of pion, kaon, and nucleon are determined by global analyses of hadron-production data in $e^+e^-$ annihilation. It is particularly important that uncertainties of the fragmentation functions are estimated for the first time. We found that light-quark and gluon fragmentation functions have large uncertainties, so that one should be careful in using these functions for hadron-production processes in heavy-ion collisions and lepton scattering. The analysis is extended to possible exotic hadron search by fragmentation functions. We found that internal structure of $f_0 (98…
A coherent study of $e^{+}e^{-}$ annihilation into two ($π^{+}π^{-}$,$K^{+}K^{-}$) and three ($π^{+}π^{-}π^{0},π^{+}π^{-}η$) pseudoscalar meson production is carried out within the framework of resonance chiral theory in energy region $E\lesssim 2 \, \mathrm{GeV}$. The work of {[}L. Y. Dai, J. Portolés, and O. Shekhovtsova, Phys. Rev. D 88,056001 (2013){]} is revisited with the latest experimental data and a joint analysis of two pseudoscalar meson production. Hence, we evaluate the lowest order hadronic vacuum polarization contributions of those two and three pseudoscalar processes to the ano…
Weak decay tree and annihilation - t-channel W - exchange amplitudes for the D0 -> K0S pi+ pi- process are calculated using quasi two-body QCD factorization approach and unitarity constraints. Final state strong kaon-pion and pion-pion interactions in S, P and D waves are described through corresponding form factors including many resonances. Preliminary results compare well with the effective mass distributions of the Belle and BABAR Collaboration analyses.
The availaible data on the D0 to K0S pi+ pi- decays are analysed in the framework of the quasi two-body QCD factorization approximation. The annihilation, via W-exchange, amplitudes are added to the weak-decay tree amplitudes. The doubly Cabibbo suppressed parts of the amplitudes are also considered. The strong interactions between the kaon-pion and pion-pion pairs in the S-, P- and D-final states are described in terms of the corresponding form factors. The kaon-pion or pion-pion scalar and vector form factors are constrained by other experimental data. Unitarity, analyticity and chiral symme…
Modern Determination of Pion and Kaon Fragmentation Functions from SIA and High-Precision COMPASS SIDIS Multiplicities
School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM)（粒子与加速器学院，基础科学研究院）；AGH University, Faculty of Physics and Applied Computer Science（AGH科技大学，物理与应用计算机科学系）；PRISMA ++ Cluster of Excellence, Institut für Physik, Johannes Gutenberg-Universität Mainz（PRISMA ++ 卓越集群，物理学研究所，约翰内斯·古腾堡美因茨大学）；Institut für Theoretische Physik, Universität Münster（理论物理研究所，明斯特大学）
We present NNFF1.0, a new determination of the fragmentation functions (FFs) of charged pions, charged kaons, and protons/antiprotons from an analysis of single-inclusive hadron production data in electron-positron annihilation. This determination, performed at leading, next-to-leading, and next-to-next-to-leading order in perturbative QCD, is based on the NNPDF methodology, a fitting framework designed to provide a statistically sound representation of FF uncertainties and to minimise any procedural bias. We discuss novel aspects of the methodology used in this analysis, namely an optimised p…
The $\textit{BABAR}$ Collaboration data of the $D^0 \to K^0_S K^+ K^-$ process are analyzed within a quasi two-body factorization framework. In earlier studies, assuming $D^0$ transitions to two kaons and the transitions between one kaon and two kaons to proceed through the dominant intermediate resonances, we approximated them as being proportional to the kaon form factors. To obtain good fits, one has to multiply the scalar-kaon form factors, derived from unitary relativistic coupled-channel models or in a dispersion relation approach, by phenomenological energy-dependent functions. The fina…
Dark matter can be gravitationally captured by the Sun after scattering off solar nuclei. Annihilations of the dark matter trapped and accumulated in the centre of the Sun could result in one of the most detectable and recognizable signals for dark matter. Searches for high-energy neutrinos produced in the decay of annihilation products have yielded extremely competitive constraints on the spin-dependent scattering cross sections of dark matter with nuclei. Recently, the low energy neutrino signal arising from dark-matter annihilation to quarks which then hadronize and shower has been suggeste…
The charge-asymmetry observed in a recent CPLEAR experiment was interpreted by the authors as a direct observation of T-noninvariance. While this is the simplest and most natural inference, and the observed effect agrees in sign and magnitude with theoretical expectation, adherents of T-invariance may argue that other interpretations are also possible. If K^0 and \bar{K}^0 are produced equally in \bar{p} p annihilation, and T-invariance is assumed to hold, the asymmetry observed in CPLEAR must be attributed to TCP-noninvariance of kaon beta-decays. If that were the case, the charge-asymmetry i…
The constraint on the ADD model of extra dimensions coming from photon annihilation into Kaluza-Klein graviton in supernova cores is revisited. In the two photon process for a conservative choice of the core parameters, we obtain the bound on the fundamental Planck scale $M_* \gtrsim$ 1.6 TeV. The combined energy loss rate due to nucleon-nucleon brehmstrahlung and photon annihilation processes is rederived, which shows that the combined bounds add only second decimal place to $M_*$. The present study can strengthen the results that are available in the current literature for the graviton emiss…
A realistic model for the free rho meson with coupling to two-pion states is employed to calculate the rho propagator in a hot and dense hadron gas. The medium modifications are based on hadronic rescattering processes: intermediate two-pion states are renormalized through interactions with surrounding nucleons and deltas, and rho meson scattering is considered off nucleons, deltas, pions and kaons. Constraints from gauge invariance as well as the full off-shell dynamics of the interactions are accounted for. Within the vector dominance model we apply the resulting in-medium rho spectral funct…
Fragmentation functions are determined for pions, kaons, and nucleons by a global analysis of charged-hadron production data in electron-positron annihilation. The optimum functions are obtained in both leading order (LO) and next-to-leading order (NLO) of alpha_s. It is important that uncertainties of the fragmentation functions are estimated in this work by the Hessian method. We found that the uncertainties are large at small Q^2 and that they are generally reduced in the NLO in comparison with the LO ones. We supply a code for calculating the fragmentation functions and their uncertainties…
Charged and neutral B decays into two charged pions and a charged or a neutral kaon are analyzed within the QCD factorization scheme where final state interactions before and after hadronization are included. The K*(892) and K*(1430) resonance effects are taken into account using the presently known pion-Kaon strange vector and scalar form factors. The weak decay amplitudes, which are calculated at leading power in Lambda_QCD/m_b and at the next-to-leading order in the strong coupling constant, include the hard scattering and annihilation contributions. The end point divergences of these weak …
Fragmentation functions are determined for the pion, kaon, and proton by analyzing charged-hadron production data in electron-positron annihilation. It is important that uncertainties of the determined fragmentation functions are estimated in this analysis. Analysis results indicate that gluon and light-quark functions have large uncertainties especially at small Q^2. We find that next-to-leading-order (NLO) uncertainties are significantly reduced in comparison with leading-order (LO) ones in the pion and kaon. The fragmentation functions are very different in various analysis groups. However,…
Fragmentation functions and their uncertainties are determined for pion, kaon, and proton by a global $χ^2$ analysis of charged-hadron production data in electron-positron annihilation and by the Hessian method for error estimation. It is especially important that the uncertainties of the fragmentation functions are estimated in this analysis. The results indicate that the fragmentation functions, especially gluon and light-quark fragmentation functions, have large uncertainties at small $Q^2$. There are large differences between widely-used functions by KKP (Kniehl, Kramer, and Pötter) and Kr…
We readdress the problem of finding a simultaneous description of the pion form factor data in e+e- annihilations and in tau decays. For this purpose, we work in the framework of the Hidden Local Symmetry (HLS) Lagrangian and modify the vector meson mass term by including the pion and kaon loop contributions. This leads us to define the physical rho, omega and phi fields as linear combinations of their ideal partners, with coefficients being meromorphic functions of s, the square of the 4--momentum flowing into the vector meson lines. This allows us to define a dynamical, i.e. s-dependent, vec…
