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High Energy Physics - Phenomenology (hep-ph)

Wed, 24 May 2023

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1.Two-pole structure of the $b_1$(1235) axial-vector meson

Authors:Samson Clymton, Hyun-Chul Kim

Abstract: We investigate the dynamical generation of the $b_1$ meson in the $\pi\omega$ interaction, using the fully off-mass-shell coupled-channel formalism with the $\pi\omega$, $\eta\rho$, $\pi\phi$, and $K\bar{K}^*$ channels included. We first construct the Feynman amplitudes for the sixteen different kernel amplitudes, considering only the $t$ and $u$ channels. Solving the coupled integral equation, we obtain the transition amplitude for the $\pi\omega$ interaction. We select the axial-vector and isovector channels from the partial-wave expansion and single out the two poles corresponding to the $b_1$ mesons: $(1306-i70)$ MeV and $(1356-i65)$ MeV. They are located below the $K\bar{K}^*$ threshold. The first pole lies below the $\eta\rho$ threshold by about 10 MeV, whereas the second one emerges above it by about 40 MeV. We analyze the effects of the two poles and background contributions to the $\pi\omega$ total cross section by using a toy model.

2.A global analysis for determined and undetermined hadronic two body weak decays of anti-triplet charmed baryons

Authors:Zhi-Peng Xing, Xiao-Gang He, Fei Huang, Chang Yang

Abstract: A large amount of data on hadronic two body weak decays of anti-triplet charmed baryons $T_{c\bar 3}$ to an octet baryon $T_8$ and an octet or singlet pseudoscalar meson $P$, $T_{c \bar 3} \to T_8 P$, have been measured. The SU(3) flavor symmetry has been applied to study these decays to obtain insights about weak interactions for charm physics. However not all such decays needed to determine the SU(3) irreducible amplitudes have been measured forbidding a complete global analysis. Previously, it has been shown that data from measured decays can be used to do a global fit to determine all except one parity violating and one parity conserving amplitudes of the relevant SU(3) irreducible amplitudes causing 8 hadronic two body weak decay channels involving $\Xi^0_c$ to $\eta$ or $\eta'$ transitions undetermined. It is important to obtain information about these decays in order to guide experimental searches. In this work using newly measured decay modes by BESIII and Belle in 2022, we carry out a global analysis and parameterize the unknown amplitudes to provide the ranges for the branching ratios of the 8 undetermined decays. Our results indicate that the SU(3) flavor symmetry can explain the measured data exceptionally well, with a remarkable minimal $\chi^2/d.o.f.$ of 1.21 and predict 80 observables in 45 decays for future experimental data to test. We then vary the unknown SU(3) amplitudes to obtain the allowed range of branching ratios for the 8 undetermined decays. We find that some of them are within reach of near future experimental capabilities. We urge our experimental colleagues to carry out related searches.

3.Structure of the medium formed in heavy ion collisions

Authors:J. R. Alvarado García, D. Rosales Herrera, A. Fernández Téllez, Bogar Díaz, J. E. Ramírez

Abstract: We investigate the structure of the medium formed in heavy ion collisions using three different models: the Color String Percolation Model (CSPM), the Core-Shell-Color String Percolation Model (CSCSPM), and the Color Glass Condensate (CGC) framework. We analyze the radial distribution function of the transverse representation of color flux tubes in each model to determine the medium's structure. Our results indicate that the CSPM behaves as an ideal gas, while the CSCSPM exhibits a structural phase transition from a gas-like to a liquid-like structure. Additionally, our analysis of the CGC framework suggests that it produces systems that behave like interacting gases for AuAu central collisions at RHIC energies and liquid-like structures for PbPb central collisions at LHC energies.

4.Study of anomalous $W^-W^+γ/Z$ couplings using polarizations and spin correlations in $e^-e^+\to W^-W^+$ with polarized beams

Authors:Amir Subba, Ritesh K. Singh

Abstract: We study the anomalous $W^-W^+\gamma/Z$ couplings in $e^-e^+\to W^-W^+$ followed by semileptonic decay using a complete set of polarization and spin correlation observables of $W$ boson with the longitudinally polarized beam. We consider a complete set of dimension-six operators affecting $W^-W^+\gamma/Z$ vertex, which are $SU(2)\times U(1)$ gauge invariant. Some of the polarization and spin correlation asymmetries average out if the daughter of $W^+$ is not tagged. We developed an artificial neural network and boosted decision trees to distinguish down-type jets from up-type jets. We obtain bounds on the anomalous couplings for center of mass energy $\sqrt{s} = 250$ GeV with integrated luminosities of~$\mathcal{L}\in\{100~\text{fb}^{-1}, 250~\text{fb}^{-1}, 1000~\text{fb}^{-1}, 3000~\text{fb}^{-1}\}$. We find that using spin-related observables and cross~section in the presence of initial beam polarization significantly improves the bounds on anomalous couplings compared to previous studies.

5.Bilinear R-parity violating supersymmetry under the light of neutrino oscillation, higgs and flavor data

Authors:Arghya Choudhury, Sourav Mitra, Arpita Mondal, Subhadeep Mondal

Abstract: In this work, we explore a well motivated beyond the Standard Model scenario, namely, R-parity violating Supersymmetry, in the context of light neutrino masses and mixing. We assume that the R-parity is only broken by the lepton number violating bilinear term. We try to fit two non-zero neutrino mass square differences and three mixing angle values obtained from the global $\chi^2$ analysis of neutrino oscillation data. We have also taken into account the updated data of the standard model (SM) Higgs mass and its coupling strengths with other SM particles from LHC Run-II along with low energy flavor violating constraints like rare b-hadron decays. We have used a Markov Chain Monte Carlo (MCMC) analysis to constrain the new physics parameter space. While doing so, we ensure that all the existing collider constraints are duly taken into account. Through our analysis we have derived the most stringent constraints possible till date with existing data on the 9 bilinear R-parity violating parameters along with $\mu$ and $\tan\beta$. We further explore the possibility of explaining the anomalous muon (g - 2) measurement staying within the parameter space allowed by neutrino, Higgs and flavor data while satisfying the collider constraints as well. We find that there still remains a small sub-TeV parameter space where the required excess can be obtained.

6.Production of Excited Doubly Heavy Baryons at the Super-$Z$ Factory

Authors:Juan-Juan Niu, Jing-Bo Li, Huan-Yu Bi, Hong-Hao Ma

Abstract: In the framework of nonrelativistic QCD, the $P$-wave excited doubly heavy baryons are thoroughly studied via the channel $e^{+} e^{-}\rightarrow \langle QQ^{\prime}\rangle[n] \rightarrow \Xi_{QQ^{\prime}} +\bar{Q^{\prime}} +\bar{Q}$, which takes place at the collision energy $Z$-pole. $Q^{(\prime)}$ represents $b$ or $c$ quark for the production of $\Xi_{cc}$, $\Xi_{bc}$, and $\Xi_{bb}$, respectively. All of the intermediate diquark states $\langle QQ'\rangle[n]$ in $P$-wave, $\langle cc\rangle[^{1}P_{1}]_{\mathbf{\bar 3}}$, $\langle cc\rangle[^{3}P_{J}]_{\mathbf{6}}$, $\langle bc\rangle[^{1}P_{1}]_{\mathbf{\bar 3}/ \mathbf{6}}$, $\langle bc\rangle[^{3}P_{J}]_{\mathbf{\bar 3}/ \mathbf{6}}$, $\langle bb \rangle[^{1}P_{1}]_{\mathbf{\bar 3}}$, and $\langle bb\rangle[^{3}P_{J}]_{\mathbf{6}}$ with $J=0$, 1, or 2, are taken into account. The cross sections and differential distributions, including the transverse momentum, rapidity, angular, and invariant mass, are discussed for the excited baryons production. The result is that the contributions of $\Xi_{cc}$, $\Xi_{bc}$, and $\Xi_{bb}$ in $P$-wave are found to be 3.97$\%$, 5.08$\%$, and 5.89$\%$, respectively, compared to $S$-wave. Supposing that all $P$-wave excited states can decay into the ground state 100\%, the total events $N_{\Xi_{cc}}=8.48 \times10^{4-6}$, $N_{\Xi_{bc}}=2.26\times10^{5-7}$, and $N_{\Xi_{bb}}=4.12 \times10^{3-5}$ would be produced at the Super-$Z$ Factory with a high luminosity up to ${\cal L} \simeq 10^{34-36}{\rm cm}^{-2} {\rm s}^{-1}$.

7.Extraction of the $x$-dependence of generalized parton distributions from exclusive photoproduction

Authors:Jian-Wei Qiu, Zhite Yu

Abstract: The $x$-dependence of hadrons' generalized parton distributions (GPDs) $\mathcal{F}(x,\xi,t)$ is the most difficult to extract from the existing known processes, while the $\xi$ and $t$ dependence are uniquely determined by the kinematics of the scattered hadron. We study the single diffractive hard exclusive processes for extracting GPDs in the photoproduction. We demonstrate quantitatively the enhanced sensitivity on extracting the $x$-dependence of various GPDs from the photoproduction cross sections, as well as the asymmetries constructed from photon polarization and hadron spin that could be measured at JLab Hall D by GlueX Collaboration and future facilities.