At LHC a large number of b-flavored baryons will be produced. In this note we propose new baryon modes to determine the photon helicity of the penguin transition $b \to s γ$. The decay $Λ_b \to Λγ$ has the drawback that the $Λ$, being neutral and long-lived, will escape detection most of the time. To overcome this difficulty, transitions of the type $Λ_b \to Λ^{*} γ$ have been proposed, where $Λ^{*}$ denotes an excited state decaying strongly within the detector into the clean mode $p K^-$. The doublet $Ξ_b$, that decays weakly, has a number of good features. The charged baryon $Ξ_b^-$ will decay into the mode $Ξ^- γ$, where the ground state hyperon $Ξ^-$, although it will decay most of the time outside the detector, can be detected because it is charged. We consider also the decay of $Ξ_b$ into $Ξ^{*} γ$, where a higher mass state $Ξ^{*}$ can decay strongly within the detector. We point out that the initial transverse polarization of $Ξ_b$ has to be known in all cases. To determine this parameter through the transition $Ξ_b \to J/Ψ Ξ$, we distinguish between different cases, and underline that in some situations one needs {\it theoretical input} on the asymmetry parameter $α_{Ξ_b}$ of the primary decay. {\it A fortiori} the same considerations apply to the case of the $Λ_b$.
In these introductory notes I give a brief overview on some theoretical aspects of light baryon spectroscopy. The first part contains a discussion of the symmetries of the baryon spectrum, the construction of flavor wave functions and some basic features of quark models. The second part examines the need for relativistic quantum field theory and focusses on spectrum calculations with functional methods.
In the version 1, we proposed a mechanism to create baryon asymmetry in a conformally sequestered supersymmetry (SUSY) breaking scenario through the Affleck-Dine (AD) mechanism. After the submission, however, we found a critical error in our discussion. This is a note on the article of version 1.
It is well known that non-abelian Yang-Mills theories present non-trivial minima of the action, the so-called instantons. In the context of electroweak theories these instanton solutions may induce violations of baryon and lepton number of the form $ΔB = ΔL = n_f$, with $n_f$ being the number of families coupled to the gauge group. An interesting feature of these violations is that the flavor structure of the gauge couplings is inherited by the instanton transitions. This effect is generally neglected in the literature. We will show that the inclusion of flavor interactions in the instanton so…
Triply heavy baryons are very interesting hadrons to be explored for they provide particular information about strong interactions, hadron structures, and weak decays of heavy baryons. We calculate the hadronic production cross sections of the Ω_{ccc} and the Ω_{ccb}, which are dominated by the gg fusion subprocesses containing 4362 and 1454 Feynman diagrams, respectively. A method for generating and calculating tree level Feynman diagrams automatically is developed to deal with complicated processes containing so many diagrams. Our results show that 10^4-10^5 events of triply heavy baryons ca…
From inclusive measurements it is known that about 7% of all $B$ mesons decay into final states with baryons. In these decays, some striking features become visible compared to mesonic decays. The largest branching fractions come with quite moderate multiplicities of 3-4 hadrons. We note that two-body decays to baryons are suppressed relative to three- and four-body decays. In most of these analyses, the invariant baryon-antibaryon mass shows an enhancement near the threshold. We propose a phenomenological interpretation of this quite common feature of hadronization to baryons.
Nucleon antinucleon annihilation into a near backward (or forward) produced meson and a high invariant mass lepton pair admits a factorized description in terms of antinucleon (or nucleon) distribution amplitudes and nucleon to meson (or antinucleon to meson) transition distribution amplitudes. We estimate the cross section of backward (and forward) pion and eta meson production in association with a high invariant mass lepton pair for the kinematical conditions of GSI-FAIR. The cross sections are found to be large enough to be measured with the PANDA detector. Interesting phenomenological app…
We have systematically studied the strong and radiative decays of the low-lying $1P$-wave doubly charmed baryons. Some interesting observations are: (i) The states $Ξ_{cc}^*$ and $Ω_{cc}^*$ with $J^P=3/2^+$ have a fairly large decay rate into the $Ξ_{cc}γ$ and $Ω_{cc}γ$ channels with a width $\sim 15$ and $\sim7$ keV, respectively. (ii) The lowest lying excited doubly charmed baryons are dominated by the $1P$ $ρ$ mode excitations, which should be quite narrow states. They decay into the ground state with $J^P=1/2^+$ through the radiative transitions with a significant ratio. (iii) The total de…
Several baryons containing a heavy b-quark, the b-baryons, have been discovered. The charmless two-body decays of b-baryons can provide a new platform for CP violating studies in a similar way as charmless two-body decays of B-meson. In b-baryon decays there are new CP violating observable related to baryon polarization. We show that in the flavor $SU(3)$ limit there exist relations involve different combinations of the decay amplitudes compared with those in CP violating rate asymmetry. These new relations therefore provide interesting tests for the mechanism of CP in the standard model (SM) …
The superfluid transition of liquid Helium shares an interesting phenomenon with the chiral limit of QCD: the specific heat is finite at the critical point, but has a cusp. From this follows an interesting mixture of universal and non-universal features at the critical point. Through the CP symmetry of chiral QCD, this has implications for the fourth order baryon number susceptibility and susceptibilities of higher orders. Investigations of such a scaling will show us whether O(4) scaling is an accurate description of baryon-free QCD when the pion mass is realistic.
In this note we collect and summarize the predictions of the Holography Inspired Stringy Hadron (HISH) model. We list the masses and widths of predicted excited states across the spectrum, based on placing the different hadrons on the non-linear Regge trajectories of a string with massive endpoints. Our predicted states include: (i) Light, heavy-light and heavy-heavy mesons. (ii) Baryons, including charmed, doubly charmed and bottom baryons. (iii) Glueballs, together with a method to disentangle them from flavorless mesons. (iv) Genuine tetraquarks, which are not "molecules" of hadrons, and ar…
Many models of meta-stable supersymmetry (SUSY) breaking lead to a very light scalar pseudo-Nambu Goldstone boson (PNGB), P, associated with spontaneous breakdown of a baryon number like symmetry in the hidden sector. Current particle physics data provide no useful constraints on the existence of P. For example, the predicted decay rates for both K --> pi + P, b--> s + P and Upsilon --> photon + P are many orders of magnitude below the present experimental bounds. We also consider astrophysical implications of the PNGB and find a significant constraint from its effect on the evolution of red g…
We review the status as regards the existence of three- and four-body bound states made of neutrons and $Λ$ hyperons. For interesting cases, the coupling to neutral baryonic systems made of charged particles of different strangeness has been addressed. There are strong arguments showing that the $Λnn$ system has no bound states. $ΛΛnn$ strong stable states are not favored by our current knowledge of the strangeness $-1$ and $-2$ baryon-baryon interactions. However, a possible $Ξ^- t$ quasibound state decaying to $ΛΛnn$ might exist in nature. Similarly, there is a broad agreement about the none…
Dark sector particles at the GeV scale carrying baryon number provide an attractive framework for understanding the origin of dark matter and the matter-antimatter asymmetry of the universe. We demonstrate that dark decays of hadronic states containing strange quarks -- hyperons -- offer excellent prospects for discovering such dark baryons. Building up on novel calculations of the matrix elements relevant for hyperon dark decays, and in view of various collider, flavor, and astrophysical constraints, we determine the expected rates at hyperon factories like BESIII and LHCb. We also highlight …
These lecture notes contain an elementary introduction to lattice QCD at nonzero chemical potential. Topics discussed include chemical potential in the continuum and on the lattice; the sign, overlap and Silver Blaze problems; the phase boundary at small chemical potential; imaginary chemical potential; and complex Langevin dynamics. An incomplete overview of other approaches is presented as well. These lectures are meant for postgraduate students and postdocs with an interest in extreme QCD. A basic knowledge of lattice QCD is assumed but not essential. Some exercises are included at the end.
We show that a recent interesting idea to circumvent the difficulties with the continuation of parton distribution functions to the Euclidean region, that consists in looking at equal time correlators between proton states of infinite momentum, encounters some problems related to the power divergent mixing pattern of DIS operators, when implemented within the lattice regularization.
Implications of Flavor Symmetries for Baryon Number Violation
Institut de Física Corpuscular (IFIC), Consejo Superior de Investigaciones Científicas (CSIC) and Universitat de València (UV)（粒子物理研究所（IFIC），西班牙国家科研理事会（CSIC）和瓦伦西亚大学（UV)）；Department of Physics, University of Basel（巴塞尔大学物理系）；Istituto Nazionale di Fisica Nucleare, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）；Dipartimento di Fisica e Astronomia ”Galileo Galilei”, Università di Padova（帕多瓦大学伽利略·伽利莱物理与天文系）；Physik-Institut, Universität Zürich（苏黎世大学物理学院）
The abundant $ψ'$ events have been collected at the Beijing Electron Positron Collider-II (BEPCII) that could undoubtedly provide us with a great opportunity to study the more attractive charmonium decays. As has been noticed before, in the process of $J/ψ$ decaying to the baryonic final states, $p K^- \barΛ$, the evident $Λ^*$ and $N^*$ bands have been observed. Similarly, by using the product of $χ_{cJ}$ from $ψ'$ radiative decay, we may confirm it or find some extra new resonances. $χ_{c0}$'s data samples will be more than $χ_{c1,2}$ taking into account the larger branching ratio of $ψ'\toγ…
We propose a new mechanism where asymmetric dark matter (ADM) and the baryon asymmetry are both generated in the same decay chain of a metastable weakly interacting massive particle (WIMP) after its thermal freeze-out. Dark matter and baryons are connected by a generalized baryon number that is conserved, while the DM asymmetry and baryon asymmetry compensate each other. This unified framework addresses the DM-baryon coincidence while inheriting the merit of the conventional WIMP miracle in predicting relic abundances of matter. Examples of renormalizable models realizing this scenario are pre…
