The LHCb Collaboration recently reported the observation of a new excited bottom baryon $Ξ_b(6227)^0$ and announced an improvement in the measurements related to the previously observed $Ξ_b(6227)^-$ state. We conduct an analysis for $Ξ_b(6227)^0$ state considering it as isospin partner of the $Ξ_b(6227)^-$ resonance and possibly $1P$ or $2S$ excited state with spin $J=\frac{3}{2}$. The corresponding masses for both possibilities have consistent results with the experimental data, indicating that only with the mass sum rules, one can not make exact decision on the nature and quantum numbers of this state. To go further, the decays of these possible excited states to $Ξ_b^- π^+$ final state are also considered and the relevant strong coupling constants are extracted from the light cone sum rules. The obtained decay width values support the possibility of $Ξ_b(6227)^0$ to be the $1P$ excited state of $Ξ_b(5945)^0$ baryon.
The developments in the experimental facilities and analyses techniques have recently lead to the observation of many hadronic states ranging from excitations of conventional hadrons to various exotic states. The baryons with single heavy quark are among these states providing an attractive field of research to get a better understanding of the nonperturbative nature of the strong interaction. Recently, the Belle Collaboration announced observation of the state $Λ_c(2910)^+$ with a mass $2913.8\pm5.6\pm3.8~\mathrm{MeV}/c^2$ and width $51.8\pm20.0\pm18.8~\mathrm{MeV}$. In the present study, by …
We discuss the issue of duality violations in hadronic tau decay. After introducing a physically motivated ansatz for duality violations, we estimate their possible size by fitting this ansatz to the tau experimental data provided by the ALEPH collaboration. Our conclusion is that these data do not exclude significant duality violations in tau decay. This may imply an additional systematic error in the value of alpha_s(m_tau), extracted from tau decay, as large as δalpha_s(m_tau) \sim 0.003-0.010 .
We suggest that the newly observed resonance Y(4260) is a $χ_{c}-ρ^0$ molecule, which is an isovector. In this picture, we can easily interpret why $Y(4260)\to π^+π^-J/ψ$ has a larger rate than $Y(4260)\to D\bar D$ which has not been observed, and we also predict existence of the other two components of the isotriplet and another two possible partner states which may be observed in the future experiments. A direct consequence of this structure is that for this molecular structure $Y(4260)\to π^+π^-J/ψ$ mode is more favorable than $Y(4260)\to K\bar KJ/ψ$ which may have a larger fraction if othe…
Inspired by the newly observed $Ω(2012)$ state at Belle II, we investigate the two-body strong decays of $Ω$ baryons up to $N=2$ shell within the chiral quark model. Our results indicate that: (i) the newly observed $Ω(2012)$ state could be assigned to the spin-parity $J^P=3/2^-$ state $|70,^210,1,1,\frac{3}{2}^-\rangle$ and the experimental data can be reasonably described. However, the spin-parity $J^P=1/2^-$ state $|70,^210,1,1,\frac{1}{2}^-\rangle$ and spin-parity $J^P=3/2^+$ state $|56,^410,2,0,\frac{3}{2}^+\rangle$ can't be completely excluded. (ii) The $D$-wave states in the $N=2$ shell…
Inspired by the newly observed $Ω_b$ states by the LHCb Collaboration, we investigate the two-body strong decays of the low-lying $λ$-mode $Ω_b$ baryons up to $N=2$ shell using the chiral quark model within the $j$-$j$ coupling scheme. Our results indicate that: (i) the newly observed states $Ω_b(6316)^-$ and $Ω_b(6330)^-$ are good candidates of the light spin $j=1$ states, while the spin-parity $J^P=1/2^-$ and $J^P=3/2^-$ cannot be distinguished. The other two states, $Ω_b(6340)$ and $Ω_b(6350)$ mostly correspond to the light spin $j=2$ states, while the spin-parity $J^P=3/2^-$ and $J^P=5/2^-…
Using the hadronic matrix elements from the lattice, B_K and xi_s, involving only the 4-quark operators for Delta flavor (F) = 2 Hamiltonian relevant for K, B_d and B_s mixing, along with V_cb, we deduce a non-trivial constraint on the SM, sin (2 beta) = 0.87+-0.09. This deviates from direct experimental measurements via the tree process, b -> c c s as well as the one via the penguin-loop b -> s decays by around 2.1 and 2.7 sigma respectively. If these deviations are confirmed they would imply the presence of new physics rather pervasively in both B_d mixing (i.e. very likely in b -> d) as wel…
$Kπ$ scattering and $K_{μ4}$ decays are studied at leading order of improved chiral perturbation theory. It is shown that high precision $K_{μ4}$ experiments at, e.g., DA$Φ$NE should allow for a direct measurement of the quark mass ratio $m_s$/${\hat m}$.
We discuss the possibility that mass effects, beyond phase space, may have substantial influence on the direct determination of $V_{tq}$ in decays of top quarks. In principle, our results are valid both for singly produced top and for $t {\bar t}$ pair production. The mass effect is practically irrelevant for the extraction of $V_{tb}$ from Tevatron data, but it may have implications for higher energy multi-jet top decay.
We reconsider the possibility that the tension in the $|V_{cb}|$ determinations from inclusive and exclusive $B$ decay modes is due to a new physics effect. We modify the Standard Model effective Hamiltonian for semileptonic $b \to c$ transitions including a tensor operator with a lepton flavour dependent coupling $ε_T^\ell$, and investigate separately the muon and electron modes. The interference term between SM and NP, proportional to the lepton mass, has different impact in the inclusive and exclusive $B$ modes to muon. Moreover, even when the lepton mass is small as for the electron, the N…
Recently, a hadronic state named $η_1(1855)$, about 1.86 GeV, was observed in the BESIII experiment. This finding has a peculiar interest due to its exotic quantum number $J^{PC}=1^{-+}$. In this paper, we examine the tetraquark interpretation for the structure of $η_1(1855)$ in the configurations of $[1_c]_{\bar{s}s}\otimes[1_c]_{\bar{q}q}$ and $[1_c]_{\bar{s}q}\otimes[1_c]_{\bar{s}q}$, and perform a mass spectrum calculation in the framework of QCD sum rules. The results show that the observed $η_1(1855)$ could be embedded into the $[1_c]_{\bar{s}s}\otimes[1_c]_{\bar{q}q}$ configuration. The…
Recently, the BES collaboration observed a broad resonant structure X(1576) with a large width being around 800 MeV and assigned its $J^{PC}$ number to $1^{--}$. We show that the isospin of this resonant structure should be assigned to 1. This state might be a molecule state or a tetraquark state. We study the consequences of a possible $K^*(892)$-${\bar κ}$ molecular interpretation. In this scenario, the broad width can easily be understood. By using the data of $B(J/ψ\to Xπ^0)\cdot B(X\to K^+K^-)$, the branching ratios $B(J/ψ\to Xπ^0)\cdot B(X\to π^+π^-)$ and $B(J/ψ\to Xπ^0)\cdot B(X\to K^+K…
We present two possibilities to determine the P-parity of the pentaquark $Θ^+$, in a model independent way, via the measurement of polarization observables in $p+p\to Θ^+ +Σ^+$, or $n+p\to Θ^+ +Λ^0$, in the near threshold region. Besides the measurement of the spin correlation coefficient, $A_{xx}=A_{yy}$, (in collisions of transversally polarized nucleons), the coefficient $D_{xx}$ of polarization transfer from the initial proton to the final $ Σ^+(Λ^0)$ hyperon is also unambiguously related to the $Θ^+$ parity.
Very recently, a new $Ω^{*}$ state was reported by the Belle Collaboration, with its mass of $2012.4 \pm 0.7\ \text{(stat)}\pm 0.6\ \text{(syst)}\ \mathrm{MeV}$, which locates just below the $KΞ^*$ threshold and hence hints to be a possible $KΞ^*$ hadronic molecule. Using the effective Lagrangian approach as the same as our previous works for other possible hadronic molecular states, we investigate the decay behavior of this new $Ω^*$ state within the hadronic molecular picture. The results show that the measured decay width can be reproduced well and its dominant decay channel is predicted to…
We consider the possibility that a large fraction of the ultrahigh energy cosmic rays are decay products of Z bosons which were produced in the scattering of ultrahigh energy cosmic neutrinos on cosmological relic neutrinos. We compare the observed ultrahigh energy cosmic ray spectrum with the one predicted in the above Z-burst scenario and determine the mass of the heaviest relic neutrino as well as the necessary ultrahigh energy cosmic neutrino flux via a maximum likelihood analysis.
In this work, we adopt the one-boson-exchange model to study the $D^{(*)}K^{(*)}$ interactions. With the same parameters, we can simultaneously reproduce the masses of the $D_{s0}(2317)$, $D_{s1}(2460)$, and $T_{c\bar{s}}^{a0(++)}(2900)$ recently observed by the LHCb collaboration in the hadronic molecular picture, where the $D_{s0}(2317)$, $D_{s1}(2460)$, and $T_{c\bar{s}}^{a0(++)}(2900)$ are regarded as the $DK[I(J^P)=0(0^+)]$, $D^*K[0(1^+)]$, and $D^*K^*[1(0^+)]$ charmed-strange molecular states, respectively. In addition, we extend to study the $Λ_cK^{(*)}$ and $Σ_cK^{(*)}$ interactions an…
We present two new extractions of the QCD coupling constant at the Z pole, $α_S(m_Z)$, from detailed comparisons of inclusive W and Z hadronic decays data to state-of-the-art perturbative Quantum Chromodynamics calculations at next-to-next-to-next-to-leading order (N$^{3}$LO) accuracy, incorporating the latest experimental and theoretical developments. In the W boson case, the total width computed at N$^{3}$LO is used for the first time in the extraction. For the Z boson pseudo-observables, the N$^{3}$LO results are complemented with the full two- and partial three-loop electroweak corrections…
Motivated by four-dimensional superstring models, we consider the possibility of treating the Yukawa couplings of the Minimal Supersymmetric Standard Model (MSSM) as dynamical variables of the effective theory at the electroweak scale. Assuming bottom-tau unification, we concentrate on the top and bottom Yukawa couplings, and find that minimizing the effective potential drives them close to an effective infrared fixed line. Requiring an acceptable bottom-top mass ratio leads in principle to an additional constraint on the MSSM parameter space. As a by-product, we give new approximate analytica…
We study process of radiative neutrino pair emission $|e\rangle \rightarrow |g \rangle + γ+ν\barν$ from coherently excited heavy ions (quantum mixture of two ionic states, the ground and an excited states) in circular motion. Determination of the neutrino mass is found to be possible with simultaneous detection of the photon and one of neutrinos in the pair down to the level of the smallest neutrino mass of order 5 meV in the three flavor scheme.
We review the determination of the QED coupling at the Z pole, which is a crucial parameter for electroweak theory. We include recent e+e- -> hadron data from Novosibirsk and Beijing to re-evaluate alpha (M_Z^2). We find 1/alpha (M_Z^2) = 128.973 +/- 0.035 or 128.934 +/- 0.040 according, respectively, to whether inclusive or exclusive e+e- -> hadron data are used in the interval 1.4 < \sqrt{s} < 2.1 GeV. The error is mainly due to uncertainties in the data in the low energy region, \sqrt{s} < 2.5 GeV. We find that no advantage is obtained by analytic continuation of the dispersion relation int…
We consider the possible role of rescattering effects in the determination of the gluon density for the LHC from DIS data. We discuss a method that uses results of s-channel calculations to estimate these effects, and comment on potential applications to diffractive and multi-parton interactions.
In this comment, we propose possible errors in constructing the continuum contribution in the sum rule studied by M. C. Birse and B. Krippa, Phys. Rev. C. {\bf 54} (1996) 3240.
We study the novel decays $B^{*}\to Bγγ$ and $D^{*}\to Dγγ$ using the framework of the Heavy Meson Chiral Lagrangian (HM$χ$L) to leading order in chiral perturbation theory. The branching ratios of these decays are expressed in terms of the strong $g_{B^{*}(D^{*})B(D)π}$ and the electromagnetic $g_{B^{*}(D^*)B(D)γ}$ couplings, thus providing a possible tool for their determination. In the charm case, using the experimentally determined ratios $({D^*}^{0,+}\to Dπ)/({D^*}^{0,+}\to Dγ),$ we are able to express the branching ratio as a function of the strong coupling only. We thus find $1.6\times …
We show that it is possible to determine the weak phase γ\equiv \arg (- V^*_{ub} V_{ud} / V^*_{cb} V_{cd}) of the Cabibbo-Kobayashi-Maskawa flavor mixing matrix only from the measurement of the color-allowed B^{\pm}_u \to D K^{\pm} decay rates. The uncertainty of this method, arising mainly from the factorization approximation for two tree-level spectator quark transitions, may be well controlled.
All couplings of a new heavy gauge boson to ordinary fermions can be determined in a model-independent way at a large $e^+e^-$ collider for large enough statistics. No such determination is possible at LEP 200, however, because its design integrated luminosity is too low for existing and forthcoming limits on $Z'$ interactions. At any rate, it should be possible to distinguish between models for $Z'$ masses $< 1\ TeV$, or to set limits of this order on $Z'$ masses for definite models. These are (preliminary) $1σ$ limits. We neglect systematic errors and assume an integrated luminosity of $0.5\…
We calculate the differential Drell-Yan production cross section in proton-nucleus collisions by including both next-to-leading order perturbative effects and effects of the nuclear medium. We demonstrate that dilepton production in fixed target experiments is an excellent tool to study initial-state parton energy loss in large nuclei and to accurately determine the stopping power of cold nuclear matter. We provide theoretical predictions for the attenuation of the Drell-Yan cross section at large values of Feynman $x_F$ and show that for low proton beam energies experimental measurements at F…
A simple method is proposed for determining the masses of new particles in collider events containing a pair of decay chains (not necessarily identical) of the form Z -> Y+1, Y -> X+2, X -> N+3, where 1,2 and 3 are visible but N is not. Initial study of a possible supersymmetric case suggests that the method can determine the four unknown masses in effectively identical chains with good accuracy from samples of a few tens of events.
Selecting the newly observed $Ξ_b(6227)^-$ by LHCb as a study example, we decode its inner structure by giving the mass spectrum analysis and the investigation of its two-body strong decay behaviors. Our result indicates that the $Ξ_b(6227)^-$ is a good candidate of the $P$-wave $Ξ_b^{\prime}$ state with $J^P=3/2^-$ or $5/2^-$. In addition, we further provide the information of the properties of the partners of the $Ξ_b(6227)^-$. These predicted states include three $2S$ states and the remaining $1P$ states in the bottom-strange baryon family. The calculated sizable Okubo-Zweig-Iizuka$-$allowe…
We show that it is possible to fully determine the neutrino mass spectrum from two-zero textures of the neutrino mass matrix. As a consequence, definite predictions can be obtained for the neutrinoless double beta decay.
We propose and apply a new approach to determining $|V_{us}|$ using dispersion relations with weight functions having poles at Euclidean (space-like) momentum which relate strange hadronic $τ$ decay distributions to hadronic vacuum polarization functions (HVPs) obtained from lattice QCD. We show examples where spectral integral contributions from the region where experimental data have large errors or do not exist are strongly suppressed but accurate determinations of the relevant lattice HVP combinations remain possible. The resulting $|V_{us}|$ agrees well with determinations from $K$ physic…
Current absolute branching fractions of $Λ_c^+$ and $D_s^+$ mesons are limiting the determination of important measurements. They have only been measured at $e^+e^-$ colliders. Here techniques for measuring them at hadron colliders are discussed. The precision determination of $Λ_c^+\to p K^-π^+$ seems possible with current data, however the corresponding determination of $D_s^+\to K^+K^-π^+$ will require more integrated luminosity.
Motivated by the newly observed resonance $X(2600)$ by BESIII Collaboration, we examine the trigluon glueball interpretation for it in the framework of QCD sum rules. We evaluate the mass spectra of the trigluon glueballs with quantum numbers $0^{-+}$ and $2^{-+}$ up to dimension 8 condensate in the operator product expansion. Our numerical results indicate that the mass of the $2^{-+}$ trigluon glueball is about $2.66\pm 0.06$ GeV, which is consistent with the mass of the X(2600) within the uncertainties, while $0^{-+}$ has a mass of $2.01\pm0.14$ GeV. The possible decay channels of the $2^{-…
I consider the two-body decay of a particle at a hadron collider into a visible and an invisible particle, generalizing $W \to e ν$, where the masses of the decaying particle and the invisible decay particle are, {\em a priori}, unknown. I prove that the transverse mass, when maximized over possible kinematic configurations, can be used to determine both of the unknown masses. I argue that the proof can be generalized to cover cases such as decays of pair-produced superpartners to the lightest, stable superpartner at the Large Hadron Collider.
The decays $χ_{b0,2}\toψψ$ and $χ_{b0,2}\toψψ\to2(μ^+μ^-)$ are considered. It is shown that with the help of $ψ$-meson angular distributions and the distributions by final muon kinematical variables it is possible to determine the spin of the decaying $χ_b$-meson. These distributions can also give an additional information about $ψ$-meson wave functions.
Very recently a new enhancement around 4.05 GeV was observed by Belle experiment. In this short note, we discuss some possible assignments for this enhancement, i.e. $ψ(3S)$ and $D^*\bar{D}^*$ molecular state. In these two assignments, Y(4008) can decay into $J/ψπ^0π^0$ with comparable branching ratio with that of $Y(4008)\to J/ψπ^+π^-$. Thus one suggests high energy experimentalists to look for Y(4008) in $J/ψπ^0π^0$ channel. Furthermore one proposes further experiments to search missing channel $D\bar{D}$, $D\bar{D}^*+h.c.$ and especially $χ_{cJ}π^+π^-π^0$ and $η_cπ^+π^-π^0$, which will be h…
The newly observed $Ξ(1620)^0$ by the Belle Collaboration inspires our interest in performing a systematic study on the interaction of an anti-strange meson $(\bar{K}^{(*)})$ with a strange or doubly strange ground octet baryon $\mathcal{B}$ ($Λ$, $Σ$, and $Ξ$), where the spin-orbit force and the recoil correction are considered in the adopted one-boson-exchange model. Our results indicate that $Ξ(1620)^0$ can be explained as a $\bar{K}Λ$ molecular state with $I(J^P)=1/2(1/2^-)$ and the intermediate force from $σ$ exchange plays an important role. Additionally, we also predict several other po…
We discuss possible options for interpreting the newly observed state Y(4140) by the CDF collaboration in $B^+\to J/ψϕK^+$ decay above the $J/ψϕ$ threshold, and argue that it is more likely to be a $D_s^*$-$D_s^*$ molecular state or an exotic ($J^{PC}=1^{-+}$) hybrid charmonium. We have discussed decay modes which would allow unambiguous identification of the hybrid charmonium option.
The relation of the strong coupling constant as measured in tau decay to other low energy determinations is considered with special attention to its impact on the question of the possible existence of light gluinos.
In SUSY scenarios with invisible LSP, sparticle masses can be determined from fits to the endpoints of invariant mass distributions. Here we discuss possible improvements by using the shapes of the distributions. Positive results are found for multiple-minima situations and for mass regions where the endpoints do not contain sufficient information to obtain the masses.
Stimulated by the recent observation of the $D_2^\ast(3000)$, we study the decay behaviors of the $3P$ and $2F$ charmed mesons in the present work. By comparing the masses and decay properties of the $3^3P_2$ and $2^3F_2$ charmed mesons with the observation of the $D_2^\ast(3000)$, we conclude that the most possible assignment of the $D_2^\ast(3000)$ is the $3^3P_2$ charmed meson, while the assignment of the $2^3F_2$ charmed meson could not be fully exclude. The results of the unobserved $3P$ and $2F$ charmed mesons in this work could provide some fundamental information of searching for these…
I report on two papers, hep-ph/9806279 and hep-ph/9807336, where complementary strategies are proposed for the determination of the chargino/neutralino sector parameters, $M_1, M_2, μ$ and $\tan β$, from the knowledge of some physical observables. This determination and the occurrence of possible ambiguities are studied as far as possible analytically within the context of the unconstrained MSSM, assuming however no CP-violation.
In this paper we show that heavy quarckonium states, similar to light mesons, form Regge trajectories in $(n,M^2)$ and $(M^2,J)$ planes and the slope of these trajectories is independent on the quantum numbers of the mesons. This fact can be useful for the prediction of the masses of heavy quarkonia and the determination of the quantum numbers of the newly discovered states.
We propose a new method to extract |Vtd/Vts| from the ratio of the decay distributions dR/ds = dB(B->Xdl+l-)/ds/dB(B->Xsl+l-)/ds. This ratio depends only on the KM ratio |Vtd/Vts| with 15% theoretical uncertainties, if dilepton invariant mass-squared s is away from the peaks of the possible resonance states, J/psi, psiprime, and etc. We also give a detailed analytical and numerical analysis on dB(B-Xql+l-)/ds (q=d,s) and dR/ds.
We discuss uncertainties and possible sources of errors associated with the determination of the diffuse Galactic gamma-ray emission using the EGRET data. Most of the issues will be relevant also in the GLAST era. The focus here is on issues that impact evaluation of dark matter annihilation signals against the diffuse gamma-ray emission of the Milky Way.
