Bottom Partners Research Articles

Heavy baryons in the relativized quark model with chromodynamics

Following the work of Capstick and Isgur [], we systematically study the mass spectrum of the heavy baryons in the relativized quark potential model with chromodynamics. Besides the original Godfrey-Isgur (GI) model, we also adopt a modified GI model which replaces the linear confinement by a screened one. The two models give similar results in our work. All heavy baryons observed so far can be explained as three-quark states. In particular, we identify the Ωc(3000)/Ωb(6316), Ωc(3050)/Ωb(6330), Ωc(3065)/Ωb(6340), and Ωc(3090)/Ωb(6350) states as the pλ excitations with quantum numbers 1/2−, 3/2−, 3/2−, and 5/2−. The Ωc(3120) is a 3/2− state with the pρ excitation, whose bottom partner is predicted to be Ωb(6446/6457,3/2−). The higher state Ωc(3188) is the 2sλ excitation with quantum numbers 1/2+, and Ωc(3327) is a dλ excitation with quantum numbers 3/2+ or 5/2+. Published by the American Physical Society 2024

Sexually transmitted infection knowledge among men who have sex with men in Nairobi, Kenya.

High rates of sexually transmitted infections (STIs) among men who have sex with men (MSM) have been reported, but there is little research on their STI knowledge. Our study sought to determine participants' characteristics that contribute to either high or low STI knowledge among MSM in Nairobi, Kenya. We mobilized MSM aged ≥18 years from Nairobi into a cross-sectional study. To determine their understanding of STIs, a pre-tested structured questionnaire was administered. Knowledge score was generated by summing up the number of responses answered correctly by a participant. We dichotomized scores as "low" and "high", by splitting the group at <12 and ≥12 which was the mean. A total of 404 participants were interviewed between March and August 2020. The mean age was 25.2 (SD = 6.4) years. Majority were single (80.4%) and Christians (84.2%). All participants had some formal education ranging from primary to tertiary; the majority (92.3%) had secondary education or more. Most (64.0%) were employed and their monthly income ranged from <50->150 USD. Almost all (98.5%) were Kenyans. Of the 404 (90.6%) self-identified as male and (47.5%) reported to be exclusively top partners. Many (39.9%) reported being versatile, while those reporting to be bottom partners were, (12.6%). The last 12 months, (55.4%) of the participants reported having sex with men only and (88.6%) reported to have had multiple sexual partners. Participants scored an average of 12.2, SD 4.5. Multivariable backward elimination logistic regression revealed that participants who had tertiary education (aOR = 0.50, 95% CI 0.32-0.77), a higher income (aOR = 0.40, 95% CI 0.22-0.75) and were engaging in vaginal sex (aOR = 1.86, 95% CI 1.25-2.78) predicted significantly higher odds of high knowledge in the final multivariable model. Participant's knowledge level regarding STIs was low. We recommend health care workers to continue educating patients about STIs.

Search for pair-produced vector-like top and bottom partners in events with large missing transverse momentum in pp collisions with the ATLAS detector

A search for pair-produced vector-like quarks using events with exactly one lepton (e or mu ), at least four jets including at least one b-tagged jet, and large missing transverse momentum is presented. Data from proton–proton collisions at a centre-of-mass energy of sqrt{s}=13 text {TeV}, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb^{-1}, are analysed. Vector-like partners T and B of the top and bottom quarks are considered, as is a vector-like X with charge +5/3, assuming their decay into a W, Z, or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section of T and B quark pairs as a function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 text {TeV} assuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 text {TeV} (1.46 text {TeV}) for exclusive T rightarrow Zt (B/X rightarrow Wt) decays. In addition, lower limits on the T and B quark masses are derived for all possible branching ratios.

Nature of the doubly-charmed tetraquark [formula omitted] in a constituent quark model

The recently discovered Tcc+ is evaluated as a DD⁎ molecular structure in the JP=1+ sector. A coupled-channels calculation in charged basis, considering the D0D⁎+, D+D⁎0 and D⁎0D⁎+ channels, is done in the framework of a constituent quark model that successfully described other molecular candidates in the charmonium spectrum such as the X(3872). The Tcc+ is found as a D0D⁎+ molecule (87%) with a binding energy of 387 keV/c2 and a width of 81 keV, in agreement with the experimental measurements. The quark content of the state forces the inclusion of exchange diagrams to treat indistinguishable quarks between the D mesons, which are found to be essential to bind the molecule. The D0D0π+ line shape, scattering lengths and effective ranges of the molecule are also analyzed, which are found to be in agreement with the LHCb analysis. We search for further partners of the Tcc+ in other charm and bottom sectors, finding different candidates. In particular, in the charm sector we find a shallow JP=1+D+D⁎0 molecule (83%), dubbed Tcc′, just 1.8 MeV above the Tcc+ state. In the bottom sector, we find an isoscalar and an isovector JP=1+ bottom partners, as BB⁎ molecules lying 21.9 MeV/c2 (I=0) and 10.5 MeV/c2 (I=1), respectively, below the B0B⁎+ threshold.

Scalar leptoquark and vector-like quark extended models as the explanation of the muon g–2 anomaly: bottom partner chiral enhancement case* *Supported by an appointment to the Young Scientist Training Program at the APCTP through the Science and Technology Promotion Fund and Lottery Fund of the Korean Government. This work was also supported by the Korean Local Governments-Gyeongsangbuk-do Province and Pohang

Leptoquark (LQ) models are well motivated solutions to the anomaly. In the minimal LQ models, only specific representations can lead to chiral enhancements. For the scalar LQs, and can lead to the top quark chiral enhancement. For the vector LQs, and can lead to the bottom quark chiral enhancement. When we consider the LQ and vector-like quark (VLQ) simultaneously, there can be more scenarios. In our previous study, we considered the scalar LQ and VLQ extended models with up-type quark chiral enhancement. Here, we study the scalar LQ and VLQ extended models with down-type quark chiral enhancement. We find two new models with B quark chiral enhancements, which originate from the bottom and bottom partner mixing. Then, we propose new LQ and VLQ search channels under the constraints of .

Roadmap to explore vectorlike quarks decaying to a new scalar or pseudoscalar

The current experimental data allow for a sub-TeV colourless weak-singlet scalar or pseudoscalar. If such a singlet field is present together with TeV-range vectorlike top and bottom partners, there is a possibility that the heavy quarks decay dominantly to the singlet state and a third-generation quark, and the singlet state decays to quark and boson pairs. Such a possibility may arise in various models but it has not been explored experimentally, especially in the context of vectorlike-quark searches. We consider some minimal models, covering the possible weak representations of the top and bottom partners, that can be mapped to many well-motivated ultraviolet-complete theories. We chart out the possible interesting and unexplored signatures of the exotic decay of vectorlike quarks and identify benchmark points representing different signal topologies for the high luminosity LHC. We perform a general scan of the parameter space with the relevant direct search bounds and find that large regions, which do not require any fine-tuning, remain open for the unexplored channels. We also perform a simple projection study in the cleanest channel and indicate how other new but experimentally challenging channels can be used to probe more regions of the parameter space.

Interpretation of the Lambda _c(2910)^+ baryon newly seen by Belle Collaboration and its possible bottom partner

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 Lambda _c(2910)^+ with a mass 2913.8pm 5.6pm 3.8~textrm{MeV}/c^2 and width 51.8pm 20.0pm 18.8~textrm{MeV}. In the present study, by the mass analyses of different excitations at Lambda _c channel and their comparison with existing experimental information, we find that the spin-parity of this newly found excited state is J^P= frac{1}{2}^- and it is a 2P state denoting by Lambda _c(frac{1}{2}^-,2P). We predict its current coupling as well, which can be served as one of the main input parameters to investigate different decays and interactions of this particle. We also determine the mass and current coupling of Lambda _b(frac{1}{2}^-,2P) as possible bottom counterpart of the new Lambda _c(2910)^+ state, which may be in agenda of different experiments in near future.

Non-resonant diagrams for single production of top and bottom partners

The search for top and bottom partners is a major focus of analyses at both the ATLAS and CMS experiments. When singly produced, these vector-like partners of the Standard Model third generation quarks retain a sizeable cross-section that makes them attractive search candidates in their respective topologies. While most efforts have concentrated on the resonant mode for single production of these hypothetical particles, the most dominant mode at narrow widths, recent studies have revealed a wide and rich phenomenology involving the non-resonant diagrams. In this letter we categorically investigate the impact of the non-resonant diagrams on different top and bottom partner single production topologies and their impact on the inclusive cross-section estimation. We also propose a parameterization for calculating the correction factor to the single vector-like quark production cross-section when such diagrams are included.

Impact of a thermal medium on newly observed Z_{cs}(3985) resonance and its b-partner

Motivated by the very recent discovery of the strange hidden-charm exotic state Z_{cs}(3985) by the BESIII Collaboration, we study the possible interpretation of this exotic state the both at T=0 and Tne 0 . We analytically compute the mass and meson-current coupling constant of this resonance with spin-parity J^{P} = 1^+ at finite temperature approximation up to the sixth order of the thermal operator dimension including non-perturbative contributions. Extracting thermal mass and meson-current coupling constant sum rules, the modifications on properties of the Z_{cs}(3985) state in hot medium are determined. As a by-product, the hadronic parameters of the bottom partner of Z_{cs}(3985) is estimated as well. The search for temperature effects on the hadronic parameters of the hidden-charm meson Z_{cs}(3985) and the bottom partner enable us to understand the phase transitions, chiral symmetry breaking, and the properties of hot-dense matter in QCD. Moreover, the full width of the resonance Z_{cs}(3985) is calculated as (12.0pm 0.8)~{mathrm {MeV}} using the strong decay in the tetraquark picture. Results for width and mass are in reasonable agreement with existing experimental data and results of other theoretical works. The information obtained about the parameters of the considered states is useful for experimental investigations of exotic mesons.

Modifications on the Properties of \(D^*_{s0}\)(2317) as Four-quark State in Thermal Medium

Since the low mass of $D^*_{s0}(2317)$ has still been a problem to the conventional quark model, one can consider other options regarding as multi-quark system. Therefore we investigate the scalar open-charm state $D^*_{s0}(2317)$ by Thermal QCD Sum Rules (TQCDSR) method using the two-point correlation function together with contributions of the non-perturbative condensates up to dimension six. Deriving and numerically analyzing thermal mass and pole residue sum rules, we accomplish the effects on the properties of $D^*_{s0}(2317)$ resonance in hot medium. Our numerical evaluations indicate that the variations in mass and pole residue values are stable through the growing temperature up to $T\cong100~\mathrm{MeV}$, but they begin to fall after this point. At critical temperature, the values of mass and pole residue change up to $91\%, 70\% $ of their values in vacuum in the molecular scenario and $ 91\%, 69\% $ in the diquark-antidiquark scenario. Our results does not give any definite information as to whether $D^*_{s0}(2317)$ resonance has molecular or diquark-antidiquark structure since they are very close to each other to differentiate them. Besides, we predict the hadronic parameters of the bottom partner of the $D^*_{s0}(2317)$ resonance in both molecular and diquark-antidiquark pictures. This bound state is worth investigating in future experiments. Also the detailed search of hot medium effects on the hadronic parameters of open-charm meson $D^*_{s0}(2317)$ and the bottom partner could have some implications to define the QCD phase diagram obtained from heavy-ion collision experiments. Moreover these results can be useful in distinguishing conventional quark model mesons from exotica.

Properties of the P c(4312) pentaquark and its bottom partner

We present an analysis of the newly observed pentaquark to shed light on its quantum numbers. To do that, the QCD sum rules approach is used. The measured mass of this particle is close to the threshold and has a small width, which supports the possibility of its being a molecular state. We consider an interpolating current in a molecular form and analyze both the positive and negative parity states with spin- . We also consider the bottom counterpart of the state with similar molecular form. Our mass result for the charm pentaquark state supports that the quantum numbers of the observed state are consistent with .

Association between relationship characteristics and willingness to use PrEP among same-sex male couples: a cross-sectional actor-partner analysis in Guangzhou, China

The association between relationship characteristics and pre-exposure prophylaxis (PrEP) acceptability among same-sex male couples has been limitedly examined. Dyadic survey data of 139 concordant HIV-negative same-sex male couples in Guangzhou, China were collected. The willingness to use PrEP was measured assuming that the participant's partner was HIV-positive. The actor-partner interdependence model was used to examine how one's relationship characteristics affected the PrEP willingness of the subject and his partner. Most participants (79.5%) were willing to use PrEP. The two individuals of the couple were distinguished by sex role in relationship, namely one usually playing the insertive role and the other usually playing the receptive role in anal intercourse. The former was labeled as "top" and the latter labeled as "bottom". The PrEP willingness of the top partner increased when he would think his partner is having sex with other people if the partner requests condom use in relationship (AOR: 5.74, 95% CI: 1.10-29.87), and decreased when his partner would get violent upon condom use requests in relationship (AOR: 0.19, 95% CI: 0.04-0.88). The PrEP willingness of the bottom partner increased when he trusted his partner (AOR: 1.13, 95% CI: 1.02-1.25) and when he or his partner disclosed the relationship to parents (AOR: 10.57, 95% CI: 1.91-58.61). Considering the sex role and relationship characteristics in couple-based interventions are important to optimize PrEP uptake among HIV-discordant same-sex male couples.

Photoproduction of strange hidden-charm and hidden-bottom states

Recently BESIII collaboration discovered a charged strange hidden-charm state Z_{cs}(3985) in the D_s^-D^{*0} + D_s^{*-}D^{0} spectrum. A higher Z'_{cs} state coupling to {bar{D}}_s^{*-}D^{*0} is expected by SU(3)-flavor symmetry, and their bottom partners are anticipated by heavy quark flavor symmetry. Here we study the photoproduction of these exotic states and investigate carefully the background from Pomeron exchange. Our results indicate that the maximal photoproduction cross section of strange partner is around 1–2 orders of magnitude smaller than that of the corresponding non-strange states. The possibility of searching for them in future electron-ion colliders (EIC) is briefly discussed.

Molecular states from D^{(*)}{bar{D}}^{(*)}/B^{(*)}{bar{B}}^{(*)} and D^{(*)}D^{(*)}/{bar{B}}^{(*)}{bar{B}}^{(*)} interactions

In this work, we preform a systematic investigation about hidden heavy and doubly heavy molecular states from the D^{(*)}{bar{D}}^{(*)}/B^{(*)}{bar{B}}^{(*)} and D^{(*)}D^{(*)}/{bar{B}}^{(*)}{bar{B}}^{(*)} interactions in the quasipotential Bethe–Salpeter equation (qBSE) approach. With the help of Lagrangians with heavy quark and chiral symmetries, interaction potentials are constructed within the one-boson-exchange model in which we include the pi , eta , rho , omega and sigma exchanges, as well as J/psi or varUpsilon exchange. Possible bound states from the interactions considered are searched for as the pole of scattering amplitude. The results suggest that experimentally observed states, Z_c(3900), Z_c(4020), Z_b(10610), and Z_b(10650), can be related to the D{bar{D}}^{*}, D^*{bar{D}}^{*}, B{bar{B}}^{*}, and B^*{bar{B}}^{*} interactions with quantum numbers I^G(J^P)=1^+(1^{+}), respectively. The D{bar{D}}^{*} interaction is also attractive enough to produce a pole with 0^+(0^+) which is related to the X(3872). Within the same theoretical frame, the existence of D{bar{D}} and B{bar{B}} molecular states with 0(0^+) are predicted. The possible D^*{bar{D}}^* molecular states with 0(0^+, 1^+, 2^+) and 1(0^+) and their bottom partners are also suggested by the calculation. In the doubly heavy sector, no bound state is produced from the DD/{bar{B}}{bar{B}} interaction while a bound state is found with 0(1^+) from DD^*/{bar{B}}{bar{B}}^* interaction. The D^*D^*/{bar{B}}^*{bar{B}}^* interaction produces three molecular states with 0(1^+), 0(2^+) and 1(2^+).

X0(2900) and X1(2900): Hadronic Molecules or Compact Tetraquarks

Very recently the LHCb collaboration reported their observation of the first two fully open-flavor tetraquark states, the X0(2900) of JP = 0+ and the X1(2900) of JP = 1−. We study their possible interpretations using the method of QCD sum rules, paying special attention to an interesting feature of this experiment that the higher resonance X1(2900) has a width significantly larger than the lower one X0(2900). Our results suggest that the X0(2900) can be interpreted as the s-wave D*–K*+ molecule state of JP = 0+, and the X1(2900) can be interpreted as the p-wave compact tetraquark state of JP = 1−. Mass predictions of their bottom partners are also given.

Special physical training of acrobats taking into account the requirements of the selected amploice (on the example of the bottom partners)

The article presents the results of introducing the program of special physical training of bottom acrobats into the training process, taking into account the requirements of the chosen position at the stage of preliminary basic training. The data obtained showed that the use of this program allows bottom acrobats to more successfully and qualitatively master the necessary skills of pair work, and also increases the response of partners as a system of bodies, which is confirmed by stabilographic studies.

Reappraisal of dark matter co-annihilating with a top or bottom partner

We revisit the calculation of relic density of dark matter particles co-annihilating with a top or bottom partner, by properly including the QCD bound-states (onia) effects of the colored partners, as well as the relevant electroweak processes which become important in the low mass region. We carefully set up the complete framework that incorporates the relevant contributions and investigate their effects on the cosmologically preferred mass spectrum, which turn out to be comparable in size to those coming from the Sommerfeld enhancement. We apply the calculation to three scenarios: bino-stop and bino-sbottom co-annihilations in supersymmetry, and a vector dark matter co-annihilating with a fermionic top partner. In addition, we confront our analysis of the relic abundance with recent direct detection experiments and collider searches at the LHC, which have important implications in the bino-stop and bino-sbottom scenarios. In particular, in the bino-stop case recent LHC limits have excluded regions of parameter with a direct detection rate that is above the neutrino floor.

Dark matter physics, flavor physics and LHC constraints in the dark matter model with a bottom partner

In the scenario that dark matter (DM) is a weakly interacting massive particle, there are many possibilities of the interactions with the Standard Model (SM) particles to achieve the relic density of DM. In this paper, we consider a simple DM model where the DM candidate is a complex scalar boson. The model contains a new complex gauge singlet scalar boson and a new fermion whose gauge charge is the same as the right-handed down-type quark. We dub the new fermion the bottom partner. These new particles have Yukawa interactions with the SM down-type quarks. The DM candidate interacts with the SM particles through the Yukawa interactions. The Yukawa interactions are not only relevant to the annihilation process of the DM but also contribute to the flavor physics, such as the ΔF = 2 processes. In addition, the flavor alignment of the Yukawa couplings is related to the decay modes of the bottom partner, and thus we can find the explicit correlations among the physical observables in DM physics, flavor physics, and the signals at the LHC. We survey the ΔF = 2 processes based on the numerical analyses of the thermal relic density, the direct detection of the DM, and the current LHC bounds. We investigate the perturbative bound on the Yukawa coupling as well. A Study of a fermionic DM model with extra scalar quarks is also given for comparison.

D -wave charmed and bottomed baryons from QCD sum rules

We study the $D$-wave charmed baryons of $SU(3)$ flavor $\mathbf{\bar3}_F$ using the method of QCD sum rule in the framework of heavy quark effective theory (HQET). We find that the $\Lambda_c(2880)$, $\Xi_c(3055)$ and $\Xi_c(3080)$ can be well described by the $D$-wave $SU(3)$ $\mathbf{\bar 3}_F$ charmed baryon multiplets of $J^P=3/2^+$ and $5/2^+$, which contain two $\lambda$-mode orbital excitations, i.e., the $\Lambda_c(2880)$ has $J^P=5/2^+$, and the $\Xi_c(3055)$ and $\Xi_c(3080)$ have $J^P = 3/2^+$ and $5/2^+$, respectively. Our results also suggest that the $\Lambda_c(2880)$ has a partner state, the $\Lambda_c(3/2^+)$ of $J^P=3/2^+$. Its mass is around $2.81 ^{+0.33}_{-0.18}$ GeV, and the mass difference between it and the $\Lambda_c(2880)$ is $28^{+45}_{-24}$ MeV. We also evaluate the masses of their bottom partners.

Explaining 750 GeV diphoton excess from top/bottom partner cascade decay in two-Higgs-doublet model extension

In this paper, we interpret the 750 GeV diphoton excess in the Zee-Babu extension of the two-Higgs-doublet model by introducing a top partner ($T$)/bottom partner ($B$). In the alignment limit, the 750 GeV resonance is identified as the heavy CP-even Higgs boson ($H$), which can be sizably produced via the QCD process $pp \to T\bar{T}$ or $pp \to B\bar{B}$ followed by the decay $T\to Ht$ or $B \to Hb$. The diphoton decay rate of $H$ is greatly enhanced by the charged singlet scalars predicted in the Zee-Babu extension and the total width of $H$ can be as large as 7 GeV. Under the current LHC constraints, we scan the parameter space and find that such an extension can account for the observed diphoton excess.