Color-sextet scalars could have an array of possible couplings to the Standard Model beyond their well known renormalizable couplings to quark pairs. The next-largest couplings these scalars might enjoy have mass dimension six, and some include electroweak fields and can therefore produce highly distinctive signals at hadron colliders. Here we study the single production of color-sextet scalars in association with a hard lepton, which results from a dimension-six coupling to leptons in addition to quarks and gluons. We identify parameter space in which these scalars decay promptly and propose a search for such particles in final states with two jets and an opposite-charge lepton pair, one member of which has high momentum. We then impose our selection criteria on the proposed signal and its leading backgrounds to project the discovery potential and exclusion limits during the next runs of the LHC. We compare our search with existing searches for leptoquarks, and we find we achieve much higher sensitivity with our tailored approach due to the unique kinematics of leptonic sextet events.
Taking a phenomenological approach, we study a color sextet scalar at the LHC. We focus on the QCD production of a color sextet pair Φ_6\barΦ_{6} through gg fusion and q\bar{q} annihilation. Its unique coupling to \bar{ψ^c}ψallows the color sextet scalar to decay into same-sign diquark states, such as Φ_6\to tt/tt^*. We propose a new reconstruction in the multijet plus same sign dilepton with missing transverse energy samples to search for on-shell tt\bar{t}\bar{t} final states from sextet scalar pair production. Thanks to the large QCD production, the search covers the sextet mass range up to…
The masses of pentaquarks $uudd\bar s$ are calculated within the framework of a semirelativistic effective QCD Hamiltonian, using a diquark picture. This approximation allows a correct treatment of the confinement, assumed here to be similar to a Y-junction. With only color antitriplet diquarks, the mass of the pentaquark candidate $Θ$ with positive parity is found around 2.2 GeV. It is shown that, if a color sextet diquark is present, the lowest $uudd\bar s$ pentaquark is characterized by a much smaller mass with a negative parity. A mass below 1.7 GeV is computed, if the masses of the color …
We investigate the production of beyond-the-standard-model color-sextet vector bosons at the Large Hadron Collider and their decay into a pair of same-sign top quarks. We demonstrate that the energy of the charged lepton from the top quark semi-leptonic decay serves as a good measure of the top-quark polarization, which, in turn determines the quantum numbers of the boson and distinguishes vector bosons from scalars.
We analyze color superconductivity of one massive flavor quark matter at moderate baryon density with a spin-zero color-sextet condensate. The most general Higgs-type ground-state expectation value of the order parameter implies complete breakdown of the SU(3)xU(1) symmetry. However, both the conventional fourth-order polynomial effective bosonic description, and the NJL-type fermionic description in the mean-field approximation favor an enhanced SO(3) symmetry of the ground state. We ascribe this finding to the failure of the mean-field approximation and propose that a more sophisticated tech…
We present the minimal sextet--quark condensation model as an attractive alternative to the standard model. The model is constructed by a simple and natural extension beyond the standard model and has many new interesting features some of which can be tested readily at the existing colliders. A crucial test may be a short--lived axion-- like $η_6$ of mass 30--60 GeV, which can produce high energy photons diffractively at hadron colliders and radiatively in $e^+ e^-$ colliders.
In this work we present an analysis of flavor violating effects mediated by color sextet scalars, which arise naturally in left-right symmetric gauge theories based on SU(2)_L \times SU(2)_R \times SU(4)_C group. The sextets, denoted here by Δ_{dd}, Delta_{ud} and Δ_{uu}, couple to right--handed quarks. We delineate the constraints on these couplings arising from meson--anti-meson transitions and flavor changing weak decays. The sextet Δ_{uu} mediates D^{0}-\bar{D}^{0} mixing via tree-level and box diagrams, and also mediates D --> K pi, pi pi decays. The sextets Δ_{ud} and Δ_{dd} mediate B_{d…
We suggest that the sextet color condensation model is not only the simplest and most attractive scheme to modify the standard model but also may already have some ``experimental" support. The crucial test may be to observe a short-- lived axion--like $η_6$ of mass around 60 GeV/$c^2$ that can produce high energy photon pairs diffractively at hadron colliders and also radiatively from $Z^0$ at high energy $e^+ e^-$ colliders. Here we show how high--energy forward scattering can be affected by diffractive production of the $η_6$. Presented to the DPF-92 meeting.
We investigate threshold resummation effects in the production of a color sextet (antitriplet) scalar at next-to-next-to-leading logarithmic (NNLL) order at the LHC in the frame of soft-collinear effective theory. We show the total cross section and the rapidity distribution with NLO+NNLL accuracy, and we compare them with the NLO results. Besides, we use recent dijet data at the LHC to give the constraints on the couplings between the colored scalars and quarks.
I introduce the critical pomeron theory ("white pomeron") proposed by Alan White, with its prediction of excessive WW and ZZ production at the LHC especially by double pomeron exchange (DPE), which is a crucial test. This theory implies dramatic effects in cosmic rays, possibly explaining the knee and high ET jet excesses. Some of the ultra high energy (UHE) cosmic rays may be "Superbaryons" made of color sextet Quarks, and most (all?) UHE collisions in the atmosphere may produce W's and Z's.
We study the factorization and resummation of the transverse momentum spectrum of the color sextet and antitriplet scalars produced at the LHC based on soft-collinear effective theory. Compared to Z boson and Higgs production, a soft function is required to account for the soft gluon emission from the final-state colored scalar. The soft function is calculated at the next-to-leading order, and the resummation is performed at the approximate next-to-next-to-leading logarithmic accuracy. The non-perturbative effects and PDF uncertainties are also discussed.
We explore the potential for discovery of an exotic color sextet scalar in same-sign top quark pair production in early running at the LHC. We present the first phenomenological analysis at colliders of color sextet scalars with full top quark spin correlations included. We demonstrate that one can measure the scalar mass, the top quark polarization, and confirm the scalar resonance with 1 inverse fb of integrated luminosity. The top quark polarization can distinguish gauge triplet and singlet scalars.
We introduce an effort to catalog the gauge-invariant interactions of Standard Model (SM) particles and new fields in a variety of representations of the SM color gauge group $\text{SU}(3)_{\text{c}}$. In this first installment, we direct this effort toward fields in the six-dimensional (sextet, $\boldsymbol{6}$) representation. We consider effective operators of mass dimension up to seven (comprehensively up to dimension six), featuring both scalar and fermionic color sextets. We use an iterative tensor-product method to identify the color invariants underpinning such operators, emphasizing s…
Adding two color sextet quarks to QCD gives many special features. The high-energy S-Matrix, constructed via reggeon diagrams and chiral anomalies, contains the Critical Pomeron and electroweak symmetry breaking is produced, by sextet pions. Cosmic ray phenomena suggest large cross-section effects will be seen at the LHC, in particular, involving the pomeron. The sextet sector embeds, uniquely, in a massless, confining, left-handed SU(5) theory. The anomaly based high-energy S-Matrix could be that of the full Standard Model.
The observed slow running of the gauge coupling in SU(3) lattice gauge theory with two flavors of color sextet fermions naturally suggests it is a theory with one relevant coupling, the fermion mass, and that at zero mass correlation functions decay algebraically. I perform a finite-size scaling study on simulation data at two values of the bare gauge coupling with this assumption and observe a common exponent for the scaling of the correlation length with the fermion mass, y_m ~ 1.5. An analysis of the scaling of valence Dirac eigenvalues at one of these bare couplings produces a similar numb…
Electroweak symmetry breaking may be a consequence of color sextet quark chiral symmetry breaking. A special solution of QCD is involved, with a high-energy S-Matrix that can be constructed ``semi-perturbatively'' via the chiral anomaly and reggeon diagrams. An infra-red fixed point and color superconductivity are crucial components of the construction. Infinite momentum physical states contain both quarks and a universal ``anomalous wee gluon'' component, and the spectrum is more limited than is required by confinement and chiral symmetry breaking. The pomeron is approximately a regge pole an…
If dynamical electroweak symmetry breaking is due to a flavor doublet of color sextet quarks, enhanced electroweak scale QCD instanton interactions may produce a large top mass, raise the $η_6$ axion mass, and also explain the excesses in the DIS cross-section at HERA and jet cross-sections at the Tevatron.
The superconductivity in cold dense QCD with three massless flavors is analyzed in the framework of the Schwinger-Dyson equation. The set of two coupled gap equations for the color antitriplet, flavor antitriplet (bar{3},bar{3}) and the color sextet, flavor sextet (6,6) order parameters is derived. It is shown that the antitriplet-antitriplet gives the dominant contribution to the color-flavor locked order parameter, while the sextet-sextet is small but nonzero.
We have carried out a Schrodinger functional (SF) calculation for the SU(3) lattice gauge theory with two flavors of Wilson fermions in the sextet representation of the gauge group. We find that the discrete beta function, which governs the change in the running coupling under a discrete change of spatial scale, changes sign when the SF renormalized coupling is in the neighborhood of g^2=2.0. The simplest explanation is that the theory has an infrared-attractive fixed point, but more complicated possibilities are allowed by the data. While we compare rescalings by factors of 2 and 4/3, we work…
We investigate whether a color-sextet scalar diquark (${\bf H}_6$) coupling to the left-handed quarks contributes to the $ΔS=2$ process. It is found that the box diagrams mediated by $W$ and ${\bf H}_6$ bosons have no contributions to $ΔS=2$ when the limit of $m_t=0$ is used, and the flavor mixing matrices for diagonalizing quark mass matrices are introduced at the same time. When the heavy top-quark mass effects are taken into account, it is found that in addition to the $W-{\bf H}_6$ box diagrams significantly contributing to $ΔS=2$, their effects can be as large as those from the ${\bf H}_6…
We study a simple model where color sextet scalars violate baryon number at tree level but do not give rise to proton decay. In particular, we include one light and two heavy sextets with $ΔB=2$ baryon number violating interactions that induce neutron anti-neutron oscillations. This setup also suggests an intimate connection to the generation of the observed baryon asymmetry in the Universe via the out of equilibrium decay of the heavy sextet scalars at around $10^{14}$ GeV. The large $SU(3)$-color charges of the scalar fields involved in generating the baryon asymmetry motivate us to study po…
We report new results for lattice gauge theories with twelve fermion flavors in the fundamental representation and two fermion flavors in the two-index symmetric (sextet) representation of the SU(3) color gauge group. Both models are important in searching for a viable composite Higgs mechanism in the Beyond the Standard Model (BSM) paradigm. We subject both models to opposite hypotheses inside and outside of the conformal window. In the first hypothesis we test chiral symmetry breaking ($χ{\rm SB}$) with its Goldstone spectrum, $F_π$, the $χ{\rm SB}$ condensate, and several composite hadron s…
If electroweak symmetry breaking is a consequence of color sextet quark chiral symmetry breaking, dramatic, large cross-section, effects are to be expected at the LHC - with the pomeron playing a prominent role. The symmetry breaking is tied to a special solution of QCD which can be constructed, at high-energy, via the chiral anomaly and reggeon diagrams. There is confinement and chiral symmetry breaking, but physical states contain both quarks and a universal, anomalous, wee gluon component. A variety of Cosmic Ray effects could be supporting evidence, including the knee in the spectrum and t…
A two flavor color sextet quark sector added to QCD yields the {\it uniquely} unitary Critical Pomeron at high energy while also producing electroweak symmetry breaking. In this paper it is argued that a number of experimental phenomena in Cosmic Ray and hadron collider physics can be interpreted as evidence for the sextet sector. These phenomena include (1) Top quark production is via the eta_6 sextet quark pseudoscalar resonance - interference with the background will produce an asymmetry. (2) Longitudinal Z pairs, produced as sextet pions, provide a high mass excess cross-section that inclu…
When the Higgs sector of the standard model is replaced by a flavor doublet of color sextet quarks, dynamical electroweak symmetry breaking occurs, with the electroweak scale identified as the sextet chiral scale. Above the electroweak scale QCD is almost scale-invariant, leading to the high-momentum enhancement of both the sextet chiral condensate and instanton interactions. The instanton interactions combine with the sextet condensate to produce electroweak scale chirality violating processes in both the triplet and sextet sectors. If the enhancement is sufficient, an electroweak scale top m…
We study orbifold compactifications of the type IIB superstring on AdS_5 x S^5/Gamma, where Gamma is the abelian group Z_8, which can lead to non-SUSY three and four family models based on quartification. In particular, we focus on two models, one fully quartified model and one a model with two trinification families and one quartification family, which reduces to the standard model with a minimal leptonic color sector.
The inclusive production of the doubly heavy baryon $Ξ_{bb}$ is investigated at polarized and unpolar- ized photon collider. bb pair in both color triplet and sextet have been considered to transform into $Ξ_{bb}$. The results indicate that the contribution from color sextet is about 8% for $Ξ_{bb}$ production. For the ILC collision energy ranging from 91GeV to 1000GeV, the total cross section of $Ξ_{bb}$ shows a downtrend, i.e., the production of $Ξ_{bb}$ has the maximal rate at $\sqrt S = 91GeV$. Our results indicate that the initial beam polarization may be an important asset for the produc…
The latest AMS-02 electron/positron precision data add to the spectrum knee as direct cosmic ray evidence for an electroweak scale strong interaction. In addition, there is significant evidence for a strong self-interaction of dark matter. QUD is a unique massless SU(5) field theory with an anomaly-generated bound-state S-Matrix that could be an unconventional origin for the Standard Model. The electroweak scale color sextet quark enhanced QCD interaction is the only new physics. Production of multiple vector bosons, that acquire masses via sextet quark pions, will give the AMS positron and el…
We extend our previous study of the SU(3) gauge theory with N_f=2 flavors of fermions in the sextet representation of color. Our tool is the Schroedinger functional method. By changing the lattice action, we push the bulk transition of the lattice theory to stronger couplings and thus reveal the beta function and the mass anomalous dimension gamma_m over a wider range of coupling, out to g^2 ~ 11. Our results are consistent with an infrared fixed point, but walking is not ruled out. Our main result is that gamma_m never exceeds 0.45, making the model unsuitable for walking technicolor. We use …
The $[SU(3)]^4$ quartification model of Babu, Ma, and Willenbrock (BMW), proposed in 2003, predicts a confining leptonic color $SU(2)$ gauge symmetry, which becomes strong at the keV scale. It also predicts the existence of three families of half-charged leptons (hemions) below the TeV scale. These hemions are confined to form bound states which are not so easy to discover at the Large Hadron Collider (LHC). However, just as $J/ψ$ and $Υ$ appeared as sharp resonances in $e^-e^+$ colliders of the 20th century, the corresponding 'hemionium' states are expected at a future $e^-e^+$ collider of th…
Structure and production of doubly charmed tetraquarks T_cc (cc ubar dbar) are studied from the viewpoint of color configurations. Based on the diquark correlation, the tetraquark T_cc with I(JP)=0(1+) is considered to be stable against strong decay. We discuss that the mixing probability of color antitriplet and sextet cc components in T_cc is suppressed by 1/m_c^2, so the two configurations are separately realized in the heavy quark limit. Utilizing the nonrelativistic QCD framework, we evaluate the production cross sections of T_cc in electron-positron collisions. The momentum dependence of…
We calculate the next-to-leading order QCD corrections to quark-quark annihilation to a scalar resonant state ("diquark") in a color representation of antitriplet or sextet at the Tevatron and LHC energies. At the LHC, we find the enhancement (K-factor) for the antitriplet diquark is typically about 1.31--1.35, and for the sextet diquark is about 1.22--1.32 for initial-state valence quarks. The full transverse-momentum spectrum for the diquarks is also calculated at the LHC by performing the soft gluon resummation to the leading logarithm and all orders in the strong coupling.
The alternative $[SU(3)]^4$ model of leptonic color and dark matter is discussed. It unifies at $M_U \sim 10^{14}$ GeV and has the low-energy subgroup $SU(3)_q \times SU(2)_l \times SU(2)_L \times SU(2)_R \times U(1)_X$ with $(u,h)_R$ instead of $(u,d)_R$ as doublets under $SU(2)_R$. It has the built-in global $U(1)$ dark symmetry which is generalized $B-L$. In analogy to $SU(3)_q$ quark triplets, it has $SU(2)_l$ hemion doublets which have half-integral charges and are confined by $SU(2)_l$ gauge bosons (stickons). In analogy to quarkonia, their vector bound states (hemionia) are uniquely sui…
We discuss near-conformal gauge theories beyond the standard model (BSM) where interesting results on the twelve-flavor $β$-function of massless fermions in the fundamental representation of the SU(3) color gauge group and dilaton tests of the light scalar with two massless fermions in the two-index symmetric tensor (sextet) representation can be viewed as parts of the same BSM paradigm under investigation. We report results from high precision analysis of the twelve-flavor $β$-function \cite{Fodor:2016zil} refuting its published IRFP \cite{Cheng:2014jba,Hasenfratz:2016dou}. We present our obj…
The $η_6$ is a ``heavy axion'' remnant of dynamical electroweak symmetry breaking by a color sextet quark condensate. Electroweak scale color instanton interactions allow it to be both very massive and yet be responsible for Strong CP conservation in the color triplet quark sector. It may have been seen at LEP via its two-photon decay mode and at TRISTAN via its hadronic decay modes.
In a version of the 3-3-1 model proposed by Duong and Ma the introduction of the scalar sextet for giving mass to the charged leptons is avoided by adding a singlet charged lepton. We show that in this case the $τ$ lepton gains mass through a seesaw--like mechanism. Besides we show how to generate neutrino masses at the tree and at the 1-loop level with the respective Maki-Nakagawa-Sakata leptonic mixing matrices.
The forward-backward asymmetry in top pair production at Tevatron has been reconfirmed by the CDF collaboration with 5.3 fb^{-1} of accumulated data. These measurements also report that the asymmetry is the largest in regions of high invariant mass M_{t\bar{t}} and rapidity difference |ΔY|. We consider light colored sextet scalars appearing in a particular non-supersymmetric \10 grand unification model within the \bar{126} scalar representation. These scalar states have masses in the range of 300 \text{GeV}-2 \text{TeV} consistent with the requirements of gauge coupling unification and bounds …
The rare processes $B_c\to D_{(s)J} ^{(*)}μ\barμ$, where $D_{(s)J}^{(*)}$ stands for the final meson $D_{s0}^*(2317)$, $D_{s1}(2460,2536)$,~$D_{s2}^*(2573)$, $D_0^*(2400)$, $D_{1}(2420,2430)$ or~$D_{2}^*(2460)$, are studied within the Standard Model. The hadronic matrix elements are evaluated in the Bethe-Salpeter approach and furthermore a discussion on the gauge-invariant condition of the annihilation hadronic currents is presented. Considering the penguin, box, annihilation, color-favored cascade and color-suppressed cascade contributions, the observables $\text{d}Br/\text{d}Q^2$, $A_{LPL}$…
We investigate simple extensions of the Mirror Twin Higgs model in which the twin color gauge symmetry and the discrete $Z_2$ mirror symmetry are spontaneously broken. This is accomplished in a minimal way by introducing a single new colored triplet, sextet, or octet scalar field and its twin along with a suitable scalar potential. This spontaneous $Z_2$ breaking allows for a phenomenologically viable alignment of the electroweak vacuum, and leads to dramatic differences between the visible and mirror sectors with regard to the residual gauge symmetries at low energies, color confinement scale…
We study anomalous high-$p_T$ baryon production in $AA$-collisions due to formation of the two parton collinear $gq$ system in the anti-sextet color state for quark jets and $gg$ system in the decuplet/anti-decuplet color states for gluon jets. Fragmentation of these states, which are absent for $NN$-collisions, after escaping from the quark-gluon plasma leads to baryon production. Our qualitative estimates show that this mechanism can be potentially important at RHIC and LHC energies.
We study a class of models in which the Higgs pair production is enhanced at hadron colliders by an extra neutral scalar. The scalar particle is produced by the gluon fusion via a loop of new colored particles, and decays into di-Higgs through its mixing with the Standard Model Higgs. Such a colored particle can be the top/bottom partner, such as in the dilaton model, or a colored scalar which can be triplet, sextet, octet, etc., called leptoquark, diquark, coloron, etc., respectively. We examine the experimental constraints from the latest Large Hadron Collider (LHC) data, and discuss the fut…
We study the stability of the different quark substructures in a quark cluster approach to pentaquark states considering the color-magnetic spin-spin interactions between quarks. The most likely configuration is found to be a triquark-diquark one where the two quarks of the diquark are coupled to spin zero and anti-triplet representations of flavor and color, and the triquark has spin one-half and belongs to the triplet representation of color and to anti-sextet of flavor. To ensure total antisymmetry under the interchange of identical particles, triquark and diquark are in relative p-wave. Us…
We study the color-dependent confining forces between two quarks by the quenched lattice simulations of Coulomb gauge QCD. The color-singlet and color-antitriplet instantaneous potentials yield attractive forces. The ratio of the string tensions obtained from them is approximately 2 and have little volume dependence. Meanwhile, the color-octet and color-sextet channels give a minor contribution for two-quark system. We finally find that the infrared self-energy of the color-nonsinglet channels diverges in the infinite volume limit; however, the degree of the divergence on the finite lattice ca…
The well-known leptonic U(1) symmetry of the standard model of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a candidate for weak-scale dark matter, as well as radiative neutrino masses. A possible key connection is a color-triplet scalar, which may be produced and detected at the Large Hadron Collider.
We analyze the compatibility of the recent LHC signals and the TeV-scale left-right model(s) in the minimal nonsupersymmetric $SO(10)$ framework. We show that the models in which the Higgs content is selected based on the extended survival hypothesis do not allow the $W_R$ boson to be at the TeV-scale. By relaxing this conjecture, we investigate various scenarios where a number of colored-scalars, originated from various Pati-Salam multiplets, are light and whence they survive down to the low energies. Performing a detailed renormalization group analysis with various low-energy Higgs configura…
Exotic hadrons are important because their existence or absence can provide important clues to understanding how QCD makes hadrons from quarks and gluons. The first experimentally confirmed exotic will be the first hadron containing both $qq$ and $\bar q q$ pairs and the first hadron containing color sextet and color octet pairs. Theoretical models are not very useful because there is no accepted model for multiquark systems with color-space correlations. The constituent quark model is the only phenomenological model with predictive power that has given experimentally tested universal predicti…
We study the masses and the leptonic decay widths of heavy quarkonium in the dual Ginzburg-Landau (DGL) theory of QCD, in which the abelian monopole condensation plays an essential role for color confinement. The effect of color screening due to the light quark pair creation is introduced by the infrared momentum cutoff in the gluon propagator. We find that the color screening effect is important to reproduce the properties of the heavy quarkonium, in particular the leptonic decay width. We also discuss the underlying systematics of the heavy quark spectroscopy in the DGL theory.
The LHC is actively searching for narrow dijet resonances corresponding to physics beyond the Standard Model. Among the many resonances that have been postulated (e.g., colored vectors, scalars, and fermions) one that would have a particularly large production rate at the LHC would be a scalar diquark produced in the s-channel via fusion of two valence quarks. In previous work, we introduced a color discriminant variable that distinguishes among various dijet resonances, drawing on measurements of the dijet resonance mass, total decay width and production cross-section. Here, we show that this…
The non-leptonic weak processes $s+u\to u+d$ and $u+d \to s+u$ are known to dominate the dissipation mechanism responsible for the viscosity of strange quark matter in its normal phase. The rates of such processes remain unknown for many color superconducting phases of quark matter. In this paper, we partially fill up the gap by calculating the difference of the rates of the two non-leptonic weak processes in four transverse spin-one color superconducting phases of quark matter (slightly) out of $β$-equilibrium. The four phases studied are the color-spin locked phase, the polar phase, the plan…
We consider the color suppressed (nonfactorizable) amplitude for the decay mode $\bar{B_{d}^0} \rightarrow π^0 π^{0} $. We treat the $b$-quark in the heavy quark limit and the energetic light ($u,d,s$) quarks within a variant of Large Energy Effective Theory combined with an extension of chiral quark models. Our calculated amplitude for $\bar{B_{d}^0} \rightarrow π^0 π^{0} $ is suppressed by a factor of order $Λ_{QCD}/m_b$ with respect to the factorized amplitude, as it should according to QCD-factorization. Further, for reasonable values of the (model dependent) gluon condensate and the const…
A minimal fermion-scalar preonic model containing two fermionic and one scalar preons is proposed. This scheme allows to prevent the occurrence of undesired SM-level particles, namely leptons and quarks with unusual electric charges. Similar to the previous FS models, color-octet leptons and color-sextet quarks, which are expected to have masses much lower than the compositeness scale, are predicted. Observation of these particles could provide first indications of preonic models. FCC (SppC) pp option will give opportunity to probe $m_{q_{6}}$ up to 48 (75) TeV and $m_{l_{8}}$ up to 15 (27) Te…
We construct simple renormalizable extensions of the standard model where the leading baryon number violating processes have $ΔB = \pm ΔL = -2$. These models contain additional scalars. The simplest models contain a color singlet and a colored sextet. For such baryon number violation to be observed in experiments, the scalars cannot be much heavier than a few TeV. We find that such models are strongly constrained by LHC physics, LEP physics, and flavor physics.
We study color allowed bottom baryon to $s$-wave and $p$-wave charmed baryon non-leptonic decays in this work. The charmed baryons include spin-1/2 and spin-3/2 states. Explicitly, we consider $Λ_b\to Λ^{(*,**)}_c M^-$, $Ξ_b\toΞ_c^{(**)} M^-$ and $Ω_b\toΩ^{(*,**)}_c M^-$ decays with $M=π, K, ρ, K^*, a_1, D, D_s, D^*, D^*_s$, $Λ^{(*,**)}_c=Λ_c, Λ_c(2595), Λ_c(2625), Λ_c(2765), Λ_c(2940)$, $Ξ_c^{(**)}=Ξ_c, Ξ_c(2815), Ξ_c(2790)$ and $Ω^{(*,**)}_c=Ω_c, Ω_c(2770), Ω_c(3050), Ω_c(3090), Ω_c(3120)$. There are six types of transitions, namely, (i) ${\cal B}_b({\bf \bar 3_f},1/2^+)$ to ${\cal B}_c({\bf…
We present the leading-color two-loop QCD corrections for the scattering of four partons and a $W$ boson, including its leptonic decay. The amplitudes are assembled from the planar two-loop helicity amplitudes for four partons and a vector boson decaying to a lepton pair, which are also used to determine the planar two-loop amplitudes for four partons and a $Z/γ^*$ boson with a leptonic decay. The analytic expressions are obtained by setting up a dedicated Ansatz and constraining the free parameters from numerical samples obtained within the framework of numerical unitarity. The large linear s…
In this work we examine the possible existence of new physics beyond the standard model which could modify the branching fractions of the leptonic (mainly tauonic) decays of bottomonium vector resonances below the $B\bar{B}$ threshold. The decay width is factorized as the product of two pieces: a) the probability of an intermediate pseudoscalar color-singlet $b\bar{b}$ state (coupling to the dominant Fock state of the Upsilon via a magnetic dipole transition) and a soft (undetected) photon; b) the annihilation width of the $b\bar{b}$ pair into two leptons, mediated by a non-standard CP-odd Hig…
The cross section of pair double heavy diquark production process $pp\to(bc)+(\bar b \bar c)+X$ is calculated in the leading order of gluonic fusion channel with all four possible color and spin combinations $[^1S_0]_{\bar3}$, $[^1S_0]_{6}$, $[^3S_1]_{\bar3}$, and $[^3S_1]_{6}$ for each of the two final diquarks taken into account. Several sources of relativistic corrections to the cross section are handled in the framework of relativistic quark model. Perturbative $\mathcal O(v^2)$ corrections originating from the production amplitude expansions in heavy quark relative velocity~$v$ depend on …
We examine the charmless hadronic B decay modes in the context of R-parity violating ($\rpv$) supersymmetry. We try to explain the large branching ratio (compared to the Standard Model (SM) prediction) of the decay $B^{\pm}\to η' K^{\pm}$. There exist data for other observed $η^{(\prime)}$ modes and among these modes, the decay $B^{0}\to ηK^{*0}$ is also found to be large compared to the SM prediction. We investigate all these modes and find that only two pairs of $\rpv$ coupling can satisfy the requirements without affecting the other $B\ra PP$ and $B\ra VP$ decay modes barring the decay $B\r…
