The observation of CP violation has been experimentally verified in numerous $B$ decays but is yet to be confirmed in final states with half-spin particles. We focus our attention on baryonic $B$-meson decays mediated dominantly through internal $W$-emission processes and show that they are promising processes to observe for the first time the CP violating effects in $B$ decays to final states with half-spin particles. Specifically, we study the $\bar B^0\to p\bar pπ^0(ρ^0)$ and $\bar B^0\to p\bar pπ^+π^-$ decays. We obtain ${\cal B}(\bar B^0\to p\bar pπ^0)=(5.0\pm 2.1)\times 10^{-7}$, in agreement with current data, and ${\cal B}(\bar B^0\to p\bar pρ^0)\simeq {\cal B}(\bar B^0\to p\bar pπ^0)/3$. Furthermore, we find ${\cal A}_{CP}(\bar B^0\to p\bar pπ^0,p\bar pρ^0,p\bar pπ^+π^-) =(-16.8\pm 5.4,-12.6\pm 3.0,-11.4\pm 1.9)\%$. With measured branching fractions ${\cal B}(\bar B^0\to p\bar pπ^0,p\bar pπ^+π^-)\sim {\cal O}(10^{-6})$, we point out that ${\cal A}_{CP}\sim -(10-20)\%$ can be new observables for CP violation, accessible to the Belle~II and/or LHCb experiments.
We study the two-body baryonic $B$ and $D_s$ decays based on the annihilation mechanism without the partial conservation of axial-vector current (PCAC) at the GeV scale. We demonstrate that the contributions of $B^-\to Λ\bar p$, $B^-\to Σ^0 \bar p$ and $\bar B^0_s\to Λ\bar Λ$ are mainly from the scalar and pseudoscalar currents with their branching ratios predicted to be around $(3.5,\,5.3,\,5.3)\times 10^{-8}$, respectively, exactly the sizes of ${\cal B}(B\to {\bf B\bar B'})$ established by the data. We also apply the annihilation mechanism to all of the charmless two-body baryonic $B$ and $…
本文讨论了在标准模型中三体重子B衰变的直接CP和T破坏。特别地，我们强调，$B^\pm\to p\bar p K^{*\pm}$中的直接CP违反不对称性约为22%，而$\bar B^0 \ra Λ\bar p π^+$中的直接$T$违反不对称性可高达12%，这对于KEK和SLAC以及SuperB和LHCb的当前B工厂是可访问的。
Supersymmetric scenarios with R-parity conservation are becoming very constrained due to the lack of missing energy signals, thus motivating those scenarios with R-parity violation. In view of this, we consider a supersymmetric model with R-parity violation and extended by an anomalous horizontal $U(1)_H$ symmetry, where a self-consistent framework with baryon-number violation is achieved along with a proper supression for lepton number violating dimension-5 operators in order to keep a proton decay safe. With the introduction of right-handed neutrinos both Dirac and Majorana masses can be acc…
The long awaited baryonic $B$ decay $\bar B{}^0\to p\bar p$ was recently observed by LHCb with a branching fraction of order $10^{-8}$. All the earlier model predictions are too large compared with experiment. In this work, we point out that for a given tree operator $O_i$, the contribution from its Fiertz transformed operator, an effect often missed in the literature, tends to cancel the internal $W$-emission amplitude induced from $O_i$. The wave function of low-lying baryons are symmetric in momenta and the quark flavor with the same chirality, but antisymmetric in color indices. Using thes…
We investigate the possibility of obtaining sizeable R-parity breaking interactions violating baryon number but not lepton number within supersymmetric grand unified theories. Such a possibility allows to ameliorate the naturalness status of supersymmetry while maintaining successful gauge coupling unification, one of its main phenomenological motivations. We show that this can be achieved without fine-tuning or the need of large representations in simple SO(10) models.
Baryonic R-parity violation arises naturally once Minimal Flavor Violation (MFV) is imposed on the supersymmetric flavor sector at the low scale. At the same time, the yet unknown flavor dynamics behind MFV could take place at a very high scale. In this paper, we analyze the renormalization group (RG) evolution of this scenario. We find that low-scale MFV is systematically reinforced through the evolution, with the R-parity violating couplings exhibiting infrared fixed points. Intriguingly, we also find that if holomorphy is imposed on MFV at some scale, it is preserved by the RG evolution. Fu…
We discuss a possibility that baryon number $B$ is spontaneously broken at low scales, of the order of MeV or even smaller, so that the neutron-antineutron oscillation can be induced at the experimentally accessible level. An associated Goldstone particle, baryonic majoron, can have observable effects in neutron to antineutron transitions in nuclei or dense nuclear matter. By extending baryon number to $B-L$ symmetry, baryo-majoron can be identified with the ordinary majoron associated with the spontaneous breaking of lepton number, with interesting implications for neutrinoless $2β$ becay wit…
The LHCb collaboration has presented first experimental evidence that spin-carrying matter and antimatter differ. The study looked at four-body decays of the $Λ_b^0$ baryon. Differences in the behaviour of matter and antimatter are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as $C\!P$ violation. We discuss purely baryonic decay processes, i.e. decay processes involving only spin-carrying particles. They are yet unexplored elementary processes. Their study opens a new chapter of flavour physics in the rou…
Lepton flavour violation (LFV) naturally occurs in many new physics models, specifically in those explaining the $B$ anomalies. While LFV has already been studied for mesonic decays, it is important to consider also baryonic decays mediated by the same quark transition. In this paper, we study LFV in the baryonic $Λ_b \to Λ\ell_1 \ell_2$ using for the first time a full basis of New Physics operators. We present expected bounds on the branching ratio in a model-independent framework and using two specific new physics models. Finally, we point out the interplay and orthogonality between the bary…
We point out that if the baryon number violating neutron-antineutron oscillation is discovered, it would impose strong limits on the departure from Einstein's equivalence principle at a level of one part in $10^{19}$. If this departure owes its origin to the existence of long-range forces coupled to baryon number $B$ (or $B-L$), it would imply very stringent constraints on the strength of gauge bosons coupling to baryon number current. For instance, if the force mediating baryon number has strength $α_B$ and its range is larger than a megaparsec, we find the limit to be $α_B \leq 2\times 10^{-…
In the scenario of cold electroweak baryogenesis, oscillations of the Higgs field lead to metastable domains of unbroken phase where the Higgs field nearly vanishes. Those domains have also been identified with the $W-t-\bar{t}$ bags, a non-topological soliton made of large number ($\sim 1000$) of gauge quanta and heavy (top and anti-top) quarks. As real-time numerical studies had shown, sphalerons (topological transition events violating the baryon number) occur only inside those bags. In this work we estimate the amount of CP violation in this scenario coming from the Standard Model, via the…
We study the rates and direct CP violations of two-body baryonic $\bar B_{u,d,s}\to {{\rm\bf B}\overline{\rm\bf B}}'$ and $B^-_c\to{{\rm\bf B}\overline{\rm\bf B}}'$ decays, where the final state baryons include low-lying octet and decuplet baryons. We incorporate topological amplitude formalism and the factorization approach. Asymptotic relations at large $m_b$ are used to simplify decay amplitudes. Using the most up-to-date data on $\bar B^0\to p\bar p$ and $B^-\toΛ\bar p$ decay rates as inputs, rates and direct CP violations of $\bar B_{u,d,s}\to {{\rm\bf B}\overline{\rm\bf B}}'$ decays are …
The sharp peak in the K+/pi+ ratio in relativistic heavy-ion collisions is discussed in the framework of the Statistical Model. In this model a rapid change is expected as the hadronic gas undergoes a transition from a baryon-dominated to a meson-dominated gas. The maximum in the Lambda/π$ ratio is well reproduced by the Statistical Model, but the change in the K+/pi+ ratio is somewhat less pronounced than the one observed by the NA49 collaboration. The calculated smooth increase of the K-/pi ratio and the shape of the Xi-/pi+ and Omega-/pi+ ratios exhibiting maxima at different incident energ…
The statistical model assuming chemical equilibriumand local strangeness conservation describes most of the observed features of strange particle production from SIS up to RHIC. Deviations are found as the maximum in the measured K+/pi+ ratio is much sharper than in the model calculations. At the incident energy of the maximum, the statistical model shows that freeze out changes regime from one being dominated by baryons at the lower energies toward one being dominated by mesons. It will be shown how deviations from the usual freeze-out curve influence the various particle ratios. Furthermore,…
Direct CP violation in $B^\pm\to p \bar{p} K^{(*)\pm}$
本文研究了标准模型中$B^\pm\to p\bar p K^{(*)\pm}$衰变的直接CP破坏。我们指出，这些三体重子B衰变可能是检测带电$B$系统中直接CP破坏的重要工具，在该系统中还没有确定的签名。特别是，我们表明，直接CP违反$B^\pm\to p\bar p K^{*\pm}$的不对称性是22%左右，支持最近的数据由BABAR协作。
Evidence for CP violation in baryonic decays has not been seen in experiments. With large data events accumulated at $e^+e^-$ collider or Large Hadron Collider, the charmed baryon decays would provide a promising laboratory to test the CP symmetry. In this work, we formulate the $Λ_c^+\toϕp$ and $ Λ_c^+\toωp$ decays for the measurements of their asymmetry parameters in weak decays at the BESIII or the LHCb experiments. The polarization transfer is analyzed in the two processes of $e^+ e^- \toΛ_c^+\barΛ_c^-$ and $Λ_b^0\to Λ^+_cπ^-$, and the formulas of the joint angular distribution for these p…
We study for the first time the three-body charmless baryonic decays $\bar B^0_s\to \bar p ΛM^+ (p \bar ΛM^-)$, with $M=π, K$. We find that the branching ratios of $\bar B^0_s\to (\bar p ΛK^+$ and $p\bar ΛK^-)$ and $\bar B^0_s\to p\bar Λπ^-$ are $(5.1\pm 1.1)\times 10^{-6}$ and $(2.8\pm 1.5)\times 10^{-7}$, respectively, which agree with recent experimental results reported by the LHCb collaboration. In addition, we derive the relations \mbox{${\cal B}(\bar B^0_s\to \bar p ΛK^+)\simeq (f_K/f_π)^2(τ_{B^0_s}/τ_{B^0}) {\cal B}(\bar B^0\to \bar p Λπ^+)$} and ${\cal B}(\bar B^0_s\to p\bar Λπ^-)/{\c…
我们指出了寻找无粲重子B衰变的新途径：与$η^\prime$有关的重子对产生很可能与两体$Kπ/ππ$模一样大，甚至稍大。我们将我们的论证以较弱的形式扩展到$B\to γ+ X_s$和$\ellν+X$。虽然计算是不可靠的，估计给出了$10^{-5}$ -$10^{-6}$阶的分支比，其中置信度是从最近的实验发现中获得的，即$B \to D^{*} p \bar n$、$D^{*} p \bar p π$并不远低于$D^*π$和$D^*ρ$的速率。对无粲重子模的观测将有助于阐明弱衰变到重子末态的动力学，而$Λ$ -重子的自我分析能力有助于CP-和T-破坏的研究。
We explore the possibility of CP violation in baryonic $Λ_b\to(Λ_c^+, p^+)π^+μ^-μ^-$ decays which are mediated by two Majorana sterile neutrino and are $|ΔL|=2$ lepton number violating processes. Appreciable CP asymmetry can be obtained if there are two on-shell Majorana neutrinos that are quasi-degenerate in mass with the mass difference of the order of average decay widths. We find that given the present constraints on the heavy to light mixing element $|V_{μN}|$, the $Λ_b\to p^+π^+μ^-μ^-$ and $Λ_b\to Λ_c^+π^+μ^-μ^-$ decay rates are suppressed but could be within the experimental reach at th…
Based on $ψ(3686)$ decays of 106 million, the 1.31 billion J/psi events and a data sample of $ψ(3770)$ with $2.9~fb^{-1}$ integrated luminosity, many analyses are performed. Exclusively baryonic decays of the $ψ(3770)$, the radiative transition $ψ(3770)\toγη_c(2S)$, the $ψ(3770)$ transition to $χ_{cJ}$, isospin violation decay $χ_{c0,2}\toπ^0η_c$, the $C-$parity violation decays $J/ψ\toγγ,γϕ$ are searched for, but no significant signals are observed, and upper limits are set for these decays. The decays of $ψ(3770)\toγχ_{c1}$ and $J/ψ\toπ^0ϕ$ signals are observed. These measurements provide mo…
We consider leptogenesis in a left-right-symmetric seesaw scenario in which neutrino mass generation and leptogenesis are dominated by the type-II seesaw term. Motivated by grand unification, we assume that the neutrino Dirac mass matrix is dominated by a single entry of the order of the top-quark mass, which leaves the low-energy phases of the lepton mixing matrix as the only sources of CP violation. Working in a regime where the triplet scalar predominantly decays into leptons, this results in a predictive scenario based on a minimal number of parameters. We perform a detailed analysis of th…
Large CP violation is an interesting phenomenon both theoretically and experimentally. Last year, LHCb Collaboration found in some three-body decays of bottom mesons that large CP violations appear in regions of the Dalitz plots that are not dominated by contributions from narrow resonances. In this paper, we present a mechanism which can induce such kind of large CP violations. In this mechanism, large localized CP asymmetries in phase space can be induced by the interference of two intermediate resonances with different spins. We also apply this mechanism to the decay channel $B^\pm\to K^\pm…
We investigate the exclusive rare baryonic $Λ_{b}\toΛ\ell^{+}\ell^{-}$ in a family non-universal $Z^{\prime}$ model, which is one of the natural extension of standard model. Using transition form factors, calculated in the framework of light cone QCD sum rules, we analyze the effects of polarized and unpolarized CP violation asymmetries for the said decay. Our results indicate that the value of unpolarized and polarized CP-violation asymmetries are considerable in both $Λ_{b}\toΛμ^{+}μ^{-}$ and $Λ_{b}\toΛτ^{+}τ^{-}$ channels and hence they give clear indication of new physics arising from the …
Direct CP violation in charmless three-body hadronic decays of $B$ mesons is studied within the framework of a simple model based on the factorization approach. Three-body decays of heavy mesons receive both resonant and nonresonant contributions. Dominant nonresonant contributions to tree-dominated and penguin-dominated three-body decays arise from the $b\to u$ tree transition and $b\to s$ penguin transition, respectively. The former can be evaluated in the framework of heavy meson chiral perturbation theory with some modification, while the latter is governed by the matrix element of the sca…
The combination Charge Conjugation-Parity-Time Reversal(CPT) is a fundamental symmetry in our current understanding of nature. As such, testing CPT violation is a strongly motivated path to explore new physics. In this paper we study CPT violation in the neutrino sector, giving for the first time a bound, for a fundamental particle, in the CPT violating particle-antiparticle gravitational mass difference. We argue that cosmology is nowadays the only data sensitive to CPT violation for the neutrino-antineutrino mass splitting and we use the latest data release from Planck combined with the curr…
We study CP violation in b-baryon decays of $Ξ_b^- \to Ξ^- D$ with $D = D^0, \bar{D}^0$ and $D_i~(i=1,2)$. We find that these baryonic decay processes provide an ideal opportunity to measure the weak phase due to the absence of the relative strong phase. Explicitly, we relate $\barρ$ and $\barη$ the CKM elements with the decay rate ratios of $R_i= Γ(Ξ_b^- \to Ξ^-D_{i} ) / Γ( Ξ_b^- \to Ξ^-D^0 )$ without the charge conjugate states. As a complementary, we also examine the decay distributions of $Λ_b \to Λ(\to p π^- ) D$. There are in total 32 decay observables, which can be parameterized by 9 re…
Direct CP violation and new physics effects in the decay mode B^+ -> phi K^+
我们研究了衰变模$B^+ \to ϕK^+$中的直接CP破坏效应。这种衰变模式主要由环诱导的$\bar b \to \bar s s \bar s$企鹅图决定，湮没图的贡献很小。因此，直接CP破坏的标准模型期望值小到可以忽略。利用QCD因子分解方法，我们发现标准模型中的CP不对称性为百分水平。在标准模型的基础上，我们考虑了两种情形，一种是带有额外矢量的下夸克模型（VLDQ），另一种是R宇称破坏的超对称模型（RPV），并证明了在$B^+ \to ϕK^+ $中直接CP破坏的不对称性在VLDQ（RPV）模型中可以达到85%（70%）.
We investigate the connection between R-parity violation (RPV) in supersymmetric models and Baryogenesis. First we discuss in detail the assumptions of a theorem by Nanopoulos and Weinberg on the CP asymmetry generated from the decay of massive particles. In light of this statement, we analyse some interesting models of Baryogenesis through RPV. We then explore, in the context of RPV SUSY, the possibility to generate the baryon asymmetry through the out-of-equilibrium decay of a metastable Weakly Interacting Massive Particle (WIMP), as proposed in \cite{Cui:2012jh}. This setting is also motiva…
Constrained flavor violation is a recent proposal for predicting the down-quark Yukawa matrix in terms of those for up quarks and charged leptons. We study the viability of CFV with respect to its predictions for the lepton mass ratios, showing that this remains a challenge, and suggest some possible means for improving this shortcoming. We then extend CFV to include neutrinos, and show that it leads to interesting predictions for hierachical heavy neutrinos, and leptogenesis dominated by decays of the second heaviest one ("N2 leptogenesis"), as well as the possibility of low-scale leptoquark-…
