The isovector and isoscalar $ND$ $s$-wave scattering lengths are extracted by fitting to the LHCb data of the $pD^0$ invariant-mass distribution in the decay $Λ_b\rightarrowπ^-pD^0$, making use of the cusp effect at the $nD^+$ threshold. The analysis is based on a coupled-channel nonrelativistic effective field theory. We find that the real part of the isovector $ND$ scattering length is unnaturally large due to the existence of a near-threshold state with a mass around 2.8 GeV. The state is consistent with the $Σ_c(2800)^+$ resonance observed at Belle. Our results suggest that it couples strongly to the $ND$ channel in an $s$-wave, and that its quantum numbers are $J^P=1/2^-$. The strong cusp behavior at the $nD^+$ threshold can be verified using updated LHCb data.
The weak phase $γ$ is extracted from three-body charmless decays of $B$ mesons following a method proposed by Bhattacharya, Imbeault \& London. The result is obtained by combining the BABAR amplitude analyses for the processes $B^0 \rightarrow K^+ π^0 π^-$, $B^0 \rightarrow K_S^0 π^+ π^-$, $B^0 \rightarrow K_S^0 K_S^0 K_S^0$, $B^0 \rightarrow K^+ K_S^0 K^-$ and $B^+ \rightarrow K^+ π^+ π^-$, under the assumption of $α_{\rm{SU(3)}}$ flavour symmetry. Six possible solutions are found. One solution is compatible with the Standard Model while the others are not. It is also found that, when average…
We fit the unfolded data of $\bar{B}^0\rightarrow D^{*+} \ell \overlineν$ from the Belle experiment, where $\ell \equiv e, μ$, using a method independent of heavy quark symmetry to extrapolate to zero-recoil and extract the value of $|V_{cb}|$. This results in $|V_{cb}| = (41.9^{~+2.0}_{~-1.9})\times 10^{-3}$, which is robust to changes in the theoretical inputs and very consistent with the value extracted from inclusive semileptonic $B$ decays.
We analyze recent $K^+$ meson photoproduction data from the CLAS collaboration for the reactions $γp\rightarrow K^+Λ$ and $γp\rightarrow K^+Σ_0$, fitting measured forward-angle differential cross sections to the form $Ae^{Bt}$. We develop a quantitative scheme for determining the kinematic region where the fit is to be done, and, from the extracted $t$-slope $B$, determine whether single-Reggeon exchange can explain the production mechanism. We find that, in the region $5 < s < 8.1$ GeV$^2$, production of the $K^+Λ$ channel can be explained by single $K^+$ Reggeon exchange, but the $K^+Σ_0$ pr…
We present a lattice QCD calculation of the $B \rightarrow D l ν$ semileptonic decay form factors $f_+(q^2)$ and $f_0(q^2)$ for the entire physical $q^2$ range. Non-relativistic QCD (NRQCD) bottom quarks and Highly Improved Staggered Quark (HISQ) charm and light quarks are employed together with $N_f = 2+1$ MILC gauge configurations. A joint fit to our lattice and BaBar experimental data allows an extraction of the CKM matrix element $|V_{cb}|$. We also determine the phenomenologically interesting ratio $R(D) = {\cal B}(B \rightarrow D τν_τ) / {\cal B}(B \rightarrow D l ν_l)$ ($l = e, μ$). We …
Diffractive dissociation processes are analysed in the framework of covariant reggeization. We have considered the general form of hadronic tensor and its asymptotic behaviour for $t\rightarrow 0$ in the case of conserved tensor currents before reggeization. Resulting expressions for differential cross-section of single dissociation (SD) process ($pp \rightarrow p M$), double dissociation (DD) ($pp\rightarrow M_1 M_2$) and for the proton-Pomeron cross-section are given in detail, and corresponding problems of the approach are discussed.
We propose to study the space-time picture of hadronization by looking at the angular distribution of photons emitted in the process e^+ e^- \rightarrow K^0 {\bar{K}}^0 γat DAΦNE energies. it is shown that the angular distributions are quite sensitive to the hadronization length.
A precise SM prediction for the direct CP violation in the $K \rightarrow ππ$ decay process is of great importance in confronting experiments and constraining new physics. The state-of-art lattice QCD study of this process will soon achieve a precision that QED effects can no longer be neglected. The inclusion of QED in such calculations is planned, and the formalism to relate the finite-volume matrix element obtained from these calculations to the physical amplitude is underway. Here, we report on the progress towards an extension of the Lellouch-Lüscher formalism in presence of QED, with the…
We discuss the possibility of extracting ${\mid}V_{cb}{\mid}$ from the future measurement at LHC of the $B_c\ {\rightarrow}\ J/ψ μ^+\ ν$ decay rate followed by the leptonic decay $J/ψ {\rightarrow}\ μ^+μ^-$. We examine in detail the influence of the measurement of the muons' momenta and vertex reconstruction in the final uncertainty of ${\mid}V_{cb}{\mid}$, as well as the required theoretical inputs at both the production and weak decay level, and their reliability in this regard. We stress the relevance of a rigorous description of the fragmentation contributions to inclusive production at la…
The influence of strong and electroweak penguin amplitudes in $B/ \bar B \rightarrow π^+π^-$ is investigated in connection with the determination of the unitarity triangle angle $α$ of the CKM matrix. A relation between the observable asymmetry, the angle $α$, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in $B^{0}\rightarrow π^{+}π^{-}$ decays is only mildly influenced by the penguin amplitudes. Experimental limits on pure penguin and penguin dominated processes are consistent with the model. This information also suggests i…
The lowest-lying resonance in the QCD spectrum is the $0^{++}$ isoscalar $σ$ meson, also known as the $f_0(500)$. We augment SU(2) chiral perturbation theory ($χ$PT) by including the $σ$ meson as an additional explicit degree of freedom, as proposed by Soto, Talavera, and Tarrús and others. In this effective field theory, denoted $χ$PT$_S$, the $σ$ meson's well-established mass and decay width are not sufficient to properly renormalize its self energy. At $\mathcal{O}(p^4)$ another low-energy constant appears in the dressed $σ$-meson propagator; we adjust it so that the isoscalar pion-pion sca…
As a consequence of the Ward identity for hadronic matrix elements, we find relations between the differential decay rates of semileptonic decay modes with the underlying quark-level transition $b\rightarrow cτν$, which are valid in scalar models. The decay-mode dependent scalar form factor is the only necessary theoretical ingredient for the relations. Otherwise, they combine measurable decay rates as a function of the invariant mass-squared of the lepton pair $q^2$ in such a way that a universal decay-mode independent function is found for decays to vector and pseudoscalar mesons, respective…
We develop a general algorithm for describing angular decay distributions in cascade decay chains of arbitrary length. The general algorithm is used to study joint angular decay distributions for the cascade decay $B\rightarrow D^{**}( \rightarrow D^*(\rightarrow D π)+π) + W(\rightarrow lν)$ where the $D^{**}$ is a generic $P$-wave charm meson state. Lepton mass effects are fully incorporated
We show that the $J/ψ\rightarrow π^{+} π^{-}$ decay is a reliable source of information for the electromagnetic form factor of the pion at $t=M_{J/ψ}^2=9.6 {\rm GeV}^2$ by using general arguments to estimate, or rather, put upper bounds on, the background processes that could spoil this extraction. We briefly comment on the significance of the resulting $F_π(M_{J/ψ}^2)$.
The results of a recent experiment measuring the reaction pp -> dK^+ \bar K^0 near threshold are interpreted in terms of a spectator model that encapsulates the main features of the observed K^+ \bar K^0 invariant mass distribution. A chi^2 fit to this data leads to an imaginary part of the isovector scattering length in the K \bar K channel of Im(a_1) = -(0.63 \pm 0.24) fm. We then use the Flatte representation of the scattering amplitude to infer a value Re(a_1) = -(0.02 \pm 0.02) fm for the real part under the assumption that scaling is approximately satisfied. We show further that it is no…
In this study, we try to extract $ωn$, $ωp$ and $ϕ$N scattering lengths from the differential cross-section data of near-threshold $ω$ and $ϕ$ photoproductions not only to the energy at threshold t$_{thr}$, but also in t to t = 0. The incoherent data of $ω$ and $ϕ$ photoproductions on deuterium target for scattering length extractions are provided by CBELSA/TAPS Collaboration and LEPS Collaboration respectively, where the deuteron is usually approximated as a weakly bound state of a quasi-free neutron plus a quasi-free proton. Under the Vector Meson Doninance model and the assumption of energy…
The final state interactions in $K^\pm\toπ^\pmπ^0π^0$ decays are considered using the methods of non-relativistic quantum mechanics. We show how to take into account the largest electromagnetic effects in the analysis of experimental data, using the amplitudes calculated earlier. We propose the relevant expressions for amplitude corrections valid both above and below the two charged pion production threshold $M_{π^0π^0}=2m_{π^\pm}$, including the average effect for the threshold bin. These formulae can be used in the procedure of pion scattering lengths measurement from $M_{π^0π^0}$ spectrum.
In light of prospects for measurements of $B_c \rightarrow D^{(\ast)} l ν$ decays in the upcoming Upgrade II of the LHC, we show that by using calculated $B_c \rightarrow D^{(\ast)}$ form factors competitive extraction of the $|V_{ub}|$ CKM matrix element from the $B_c \to D μ\barν_μ$ decay might be possible. To minimize experimental and theoretical uncertainties we provide the ratio $|V_{ub}|/|V_{cb}|$ by normalizing the $B_c \rightarrow D^{(\ast)} μ\barν_μ$ to $B_c \to J/ψμ\barν_μ$ decay. We also briefly examine the suggestion to extract $|V_{ub}|/|V_{cs}|$ from the theoretically interesting…
A width difference of the order of 20\% has previously been predicted for the two mass eigenstates of the $B_s$ meson. The dominant contributor to the width difference is the $b\rightarrow c\bar c s$ transition, with final states common to both $B_s$ and $\overline{B}_s$. All current experimental analyses fit the time-dependences of flavor-specific $B_s$-modes to a single exponential, which essentially determines the average $B_s$ lifetime. We stress that the same data sample allows even the measurement of the width difference. To see that, this note reviews the time-dependent formulae for tag…
Neutrinoless double beta decay (\( 0 νββ\)) is a hypothetical nuclear decay mode with important implications. In particular, observation of this decay would demonstrate that the neutrino is a Majorana particle and that lepton number conservation is violated in nature. Relating experimental constraints on \(0 νββ\) decay rates to the neutrino masses requires theoretical input in the form of non-perturbative nuclear matrix elements which remain difficult to calculate reliably. This work marks a first step toward providing a general lattice QCD framework for computing long-distance \(0 νββ\) matr…
We suggest the most model-independent and simple description of the $γγ\rightarrowππ$ process near threshold in framework of S-matrix approach. The amplitudes contain the pion polarizabilities and rather restricted information about $ππ$ interaction. Application of these formulae for description of MARK-II \cite{M2} and Crystal Ball \cite{CB} data gives: $(α-β)^{C}=(6.0\pm 1.2)\cdot 10^{-42} {\rm cm}^{3}$, $(α-β)^{N}=(-1.4\pm 2.1)\cdot 10^{-42} cm^3$ (in units system $e^2 = 4 πα$) at the experimental values of $ππ$ scattering lengths. Both values are compartible with current algebra prediction…
We reanalyze the extraction of the heavy Higgs boson signal $H\rightarrow W^+W^-\rightarrow \bar\ellν,\ell\barν$ $(\ell=e\hbox{ or }μ)$ from the Standard Model background at hadron supercolliders, taking into account revised estimates of the top quark background. With new acceptance criteria the detection of the signal remains viable. Requiring a forward jet-tag, a central jet-veto, and a large relative transverse momentum of the two charged leptons yields $S/\sqrt B>6$ for one year of running at the SSC or LHC.
We extract the proton charge radius from the elastic form factor (FF) data using a novel theoretical framework combining chiral effective field theory and dispersion analysis. Complex analyticity in the momentum transfer correlates the behavior of the spacelike FF at finite $Q^2$ with the derivative at $Q^2 = 0$. The FF calculated in the predictive theory contains the radius as a free parameter. We determine its value by comparing the predictions with a descriptive global fit of the spacelike FF data, taking into account the theoretical and experimental uncertainties. Our method allows us to u…
We discuss the feasibility of the observation of the signal from $B_c$ mesons in the ATLAS experiment at the LHC. In particular, we address the decay mode $B_c{\rightarrow}J/ψπ$ followed by the leptonic decay $J/ψ{\rightarrow}μ^+μ^-$, which should permit an accurate measurement of the $B_c$ mass. We performed a Monte Carlo study of the signal and background concluding that a precision of $\approx$ 1 MeV for the $B_c$ mass could be achieved after one year of running at $\lq\lq$low" luminosity. The semileptonic decay $B_c{\rightarrow}J/ψ μ^+ν_μ$ is also considered for a possible extraction of ${…
Experimental values of the lifetime of the 1s level of pionium and of the difference between the energies of the 2s and 2p levels yield values of the a(0c) and a(cc) elements of the s-wave scattering matrix for the 2-channel (pi+ pi-, pi0 pi0) system at the pi+ pi- threshold. We develop a method for obtaining the isospin invariant quanties a20 - a00 and 2a00 + a20 from a(0c) and a(cc). We emphasize that the isospin invariant scattering lengths a00 and a20 universally used in the literature cannot be considered to be purely hadronic quantities.
The transition helicity amplitudes from the proton ground state to the $P_{11}(1440)$ and $D_{13}(1520)$ excited states ($γ_{v}pN^*$ electrocouplings) were determined from the analysis of nine independent one-fold differential $π^{+} π^{-} p$ electroproduction cross sections off a proton target, taken with CLAS at photon virtualities 0.25\enskip {\rm GeV$^{2}$} $<$ $Q^{2}$ $<$ 0.60 \enskip {\rm GeV$^{2}$}. The phenomenological reaction model was employed for separation of the resonant and non-resonant contributions to the final state. The $P_{11}(1440)$ and $D_{13}(1520)$ electrocouplings were…
$D\rightarrow π$ transitions from QCD Light-Cone Sum Rules with the chiral currents
Institute of Theoretical Physics, College of Physics and Electronic Engineering, Northwest Normal University（西北师范大学物理与电子工程学院理论物理研究所）；Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所）；Lebedev Physical Institute, Russian Academy of Sciences（俄罗斯科学院列别杰夫物理研究所）；General Education Center, Qinghai Institute of Technology（青海理工学院公共教学中心）；School of Nuclear Science and Technology, University of Chinese Academy of Sciences（中国科学院大学核科学与技术学院）；CAS Key Laboratory of High Precision Nuclear Spectroscopy, Institute of Modern Physics, Chinese Academy of Sciences（中国科学院近代物理研究所高精度核谱学国家重点实验室）；Lanzhou Center for Theoretical Physics, Lanzhou University（兰州大学兰州理论物理中心）
