We report the first observation of two resonance-like structures in the pi+ chi_c1 invariant mass distribution near 4.1 GeV/c^2 in exclusive B0-bar --> K- pi+ chi_c1 decays. From a Dalitz plot analysis in which the pi+ chi_c1 mass structures are represented by Breit-Wigner resonance amplitudes, we determine masses and widths of: M_1 = (4051 +-14 +20-41) MeV/c^2, Gamma_1 = (82 +21-17 +47-22) MeV, M_2 = (4248 +44-29 +180-35}) MeV/c^2, and Gamma_2 =(177 +54-39 +316-61) MeV; and product branching fractions of BF(B0-bar --> K- Z+_1,2) x BF(Z+_1,2 --> pi+ chi_c1) = (3.0 +1.5-0.8 +3.7-1.6) x 10^-5 and (4.0 +2.3-0.9 +19.7-0.5) x 10^-5 respectively. Here the first uncertainty is statistical, the second is systematic. The significance of each of the pi+ chi_c1 structures exceeds 5 sigma, including the systematic uncertainty from various fit models. This analysis is based on 657 x 10^6 BB-bar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
We study exclusive chi_c0, chi_c1 and chi_c2 decays to four-hadron final states involving two charged and two neutral mesons: pi^+pi^-pi^0pi^0, K^+K^-pi^0pi^0, pppi^0pi^0, K^+K^-etapi^0, and K^+-pi^-+K^0pi^0o. The chi_c states are produced in radiative decays of 3.08 million psi-prime resonance decays and observed in the CLEO detector. We also measure the largest substructure contributions to the modes pi^+pi^-pi^0pi^0 and K^+-pi^-+K^0pi^0.
Using a sample of 2.59 \times 10^7 psi(2S) decays collected by the CLEO--c detector, we present results of a study of chi_{cJ} (J=0,1,2) decays into baryon-antibaryon final states. We present the world's most precise measurements of the chi_cJ -> p-pbar and chi_cJ -> Lambda-Lambdabar branching fractions, and the first measurements of chi_c0 decays to other hyperons. These results illuminate the decay mechanism of the chi_c states.
In CDF we have observed several exclusive processes: 2-photon --> e+e- and --> mu+mu-, photon+pomeron --> J/psi and psi(2S), and pomeron+pomeron --> chi_c. The cross sections agree with QED, HERA photoproduction data, and theoretical estimates of gg --> chi_c with another gluon exchanged to screen the color. This observation of exclusive chi_c, together with earlier observations of exclusive dijets and exclusive 2-photon candidates, support some theoretical predictions for p+p --> p+H+p at the LHC. Exclusive dileptons offer the best means of precisely calibrating forward proton spectrometers.
Using a sample of 2.59 times 10^7 psi(2S) decays collected by the CLEO--c detector, we present results of a study of chi_{c0} and chi_{c2} decays into two-meson final states. We present the world's most precise measurements of the chi_{cJ,(J=0,2)} -> pi^+pi^-, pi^0 pi^0, K^+K^-, K^0_S K^0_S, eta eta and eta^{prime} eta^{prime} branching fractions, and a search for chi_c decays into eta eta^{prime}. These results shed light on the mechanism of charmonium decays into pseudoscalar mesons.
We perform a study of the exclusive production of $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ in initial-state-radiation events, from $e^+ e^-$ annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium and possible new resonances. The data sample corresponds to an integrated luminosity of 384 $fb^{-1}$ and was recorded by the BaBar experiment at the PEP-II storage rings. The $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ mass spectra show clear evidence of several $ψ$ resonances. However, there is no evidence for $Y(4260) \to D \bar D^*$ or $Y(4260)\to D^* \bar D^*$.
The exclusive production of baryon-antibaryon pairs in the collisions of two quasi-real photons has been studied using different detectors at e+e- colliders. Results are presented for $γγ\to$ proton antiproton, $γγ\toΛ\barΛ$, and $γγ\to Σ^{0}\bar{Σ^{0}}$ final states. The cross-section measurements are compared with all the existing experimental data and with the analytic calculations based on the three-quark model, on the quark-diquark model, and on the handbag model.
Using data collected by the CLEO detector in the Upsilon(4S) region, we report new measurements of the exclusive decays of B mesons into final states of the type Lambda_c^+ p-bar n(pi), where n=0,1,2,3. We find signals in modes with one, two and three pions and an upper limit for the two body decay Lambda_c^+ pbar. We also make the first measurements of exclusive decays of B mesons to Sigma_c p-bar n(pi), where n=0,1,2. We find signals in modes with one and two pions and an upper limit for the two body decay Sigma_c p-bar. Measurements of these modes shed light on the mechanisms involved in B …
A search for central exclusive production of top quark pairs ($\mathrm{t}\bar{\mathrm{t}}$) is presented using collision data collected by CMS and the CMS-TOTEM Precision Proton Spectrometer in 2017. A data-driven method to estimate the background from coincidences of inclusive events and pileup protons is described, as well as the development of a Boosted Decision Tree classifier to separate the exclusive $\mathrm{t}\bar{\mathrm{t}}$ signal from the inclusive $\mathrm{t}\bar{\mathrm{t}}$ background. The first-ever upper limits on the cross section of exclusive $\mathrm{t}\bar{\mathrm{t}}$ are…
We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the D0 experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is $2 \times 10^{-5}$, corresponding to a 4.1 standard deviation significance.
We report the first observation of the exclusive decays \bar B\to D^{(*)}K^{*-}, using 9.66 x 10^{6} B\bar{B} pairs collected at the Υ(4S) with the CLEO detector. We measure the following branching fractions: {\cal B}(B^- -> D^0 K^{*-})=(6.1 +- 1.6 +-1.7)x10^{-4}, {\cal B}(\bar{B^0} -> D^+K^{*-})=(3.7 +- 1.5 +- 1.0) x 10^{-4}, {\cal B}(\bar{B^0} -> D^{*+}K^{*-})=(3.8 +- 1.3 +- 0.8) x 10^{-4} and {\cal B}(B^- --> D^{*0} K^{*-})=(7.7 +- 2.2 +- 2.6) x 10^{-4}. The \bar B ->D^*K^{*-} branching ratios are the averages of those corresponding to the 00 and 11 helicity states. The errors shown are sta…
New Babar results on exclusive e+e- -> hadrons reactions at low c.m. energy with a baryon-antibaryon or K\bar{K} pair in the final state are presented. Cross sections are measured using the initial state radiation technique from the threshold up to 4--5 GeV. From the measured e+e- -> proton\antiproton, Lambda\Lbar, Sigma0\Sigbar0, Lambda\Sigbar0(Sigma0\Lbar) cross sections we derive effective baryon form factors and compare them with predictions. We measure the K\bar{K}π(η), K+K-ππ, K+K-3π, K+K-4π, K+K-K+K- final states and also study their internal structure. A new Y(2175) state is observed i…
A study of exclusive production of the $D \bar D$ system through initial-state r adiation is performed in a search for charmonium states, where $D=D^0$ or $D^+$. The $D^0$ mesons are reconstructed in the $D^0 \to K^- π^+$, $D^0 \to K^- π^+ π^0$, and $D^0 \to K^- π^+ π^+ π^-$ decay modes. The $D^+$ is reconstructed through the $D^+ \to K^- π^+ π^+$ decay mode. The analysis makes use of an integrated luminosity of 288.5 fb$^{-1}$ collected by the BaBar experiment. The $D \bar D$ mass spectrum shows a clear $ψ(3770)$ signal. Further structures appear in the 3.9 and 4.1 GeV/$c^2$ regions. No evide…
The status of exclusive two-body and three-body baryonic B decays is reviewed. The threshold peaking effect in baryon pair invariant mass is stressed and explained. Weak radiative baryonic B decays mediated by the electromagnetic penguin process are discussed.
We report the results of a search for the rare baryonic decay modes B -> Lambda Lambdabar, B -> Lambdabar p, B -> Lambdabar p pi, and B -> p pbar using 5.8M BBbar pairs collected with the CLEO detector. We see no statistically significant signals in any of these modes and set 90% confidence level upper limits on their branching fractions, B(B -> Lambda Lambdabar) < 3.9 \times 10^{-6}, B(B -> Lambdabar p) < 2.6 \times 10^{-6}, B(B -> Lambdabar p pi) < 1.3 \times 10^{-5}, and B(B -> p pbar) < 7.0 \times 10^{-6}.
Using 29.1fb-1 of data accumulated at the Upsilon(4S) with the Belle detector at KEKB, we have studied the decay modes B0bar->Lambda_c+ pbar pi+pi-, B- -> Lambda_c+ pbar pi-, and B0bar ->Lambda_c+ pbar. We report branching fractions of exclusive B decays to charmed baryons with four-, three- and two-body final states, including intermediate Sigma_c++ and Sigma_c0 states. We observed B0bar -> Sigma_c(2455)++pbar pi- for the first time with a branching fraction of (2.38+0.63-0.55+-0.41+-0.62)x10-4 and observed evidence for the two-body decay B- ->Sigma_c(2455)0 pbar with a branching fraction of …
A search for fully reconstructed Lambda_b baryons was performed, using about 3.5x10^6 hadronic Z0 decays acquired by the DELPHI detector at LEP-1. Two event candidates were found in the colour-suppressed decay channel J/psi Lambda, and four in the colour-allowed channels Lambda_c pi/a1, with an estimated background of 0.25 and 1.05 events, respectively. Measurements of the Lambda_b mass yield (5612.1 +- 21.2 +- 6.0) MeV and (5610 +- 24 +- 16) MeV, respectively, and are consistent with the world average value of PDG.
We report on the measurement of the central exclusive production process $pp \ \rightarrow \ pXp$ in proton-proton collisions at RHIC with the STAR detector at $\sqrt{\mathrm{s}} = 510$ GeV. At this energy, this process is dominated by a double Pomeron exchange mechanism. The tracks of the centrally produced system $X$ were reconstructed in the central detector of STAR, the Time Projection Chamber and the Time of Flight systems, and were identified using the ionization energy loss and the time of flight method. The diffractively scattered protons, moving intact inside the RHIC beam pipe after …
We consider the exclusive decays $B \to D^{(*)}\,\ell \barν$ and study the effect of non $V-A$ structures on the observables. We extend the standard model hadronic current by additional right-handed vector as well as left- and right-handed scalar and tensor contributions and calculate the decay rates including the perturbative corrections up to order $α_s$. Using the data of the exclusive semileptonic $b \to c $ decays and recent calculations of the form factors at the non-recoil point we discuss the constraints to the wrong helicity admixtures in the hadronic current.
The $b \rightarrow s γ$, $b \rightarrow d γ$ and $b \rightarrow s \ell^+ \ell^-$ processes are allowed at higher order via the electroweak loop or box diagrams in the Standard model. It is sensitive probe to search for new physics beyond the Standard model because new particles might enter in the loop. We present preliminary results of branching fraction of the $\bar{B} \rightarrow X_s γ$, $CP$ asymmetry in the $\bar{B} \rightarrow X_{s+d} γ$, and the forward-backward asymmetry in the $\bar{B} \rightarrow X_s \ell^+ \ell^-$. The results are based on a data sample containing $772 \times 10^6 B\…
We report on exclusive decays of B mesons into final states containing charmonium using data collected with the BABAR detector at the PEP-II storage rings. The charmonium states considered here are J/psi, psi(2S), and chi_C1. Branching fractions for several exclusive final states, a measurement of the decay amplitudes for the B0 --> J/psi K* decay, and measurements of the B0 and B+ masses are presented. All of the results we present here are preliminary.
Using data accumulated with the CLEO detector corresponding to an integrated luminosity of 5.63 pb^-1 on the peak of the psi(2S) and 20.70 pb^-1 continuum at 3.67 GeV, we report first measurements of the branching fractions for the following 13 decay modes of the psi(2S): eta 3pi, eta^\prime 3pi, rho K^+K^-, K^+K^-pi^+pi^-pi^0, 2(K^+K^-), 2(K^+K^-)pi^0, rho p \bar p, p \bar p pi^+pi^-pi^0, eta p \bar p, p \bar p K^+K^-, Lambda \bar Lambda pi^+pi^-, Lambda \bar p K^+, Lambda \bar p K^+pi^+pi^-, and more precise measurements of 8 previously measured modes: 2(pi^+pi^-), rho pi^+pi^-, 2(pi^+pi^-)p…
The status of exclusive two-body and three-body baryonic B decays is reviewed. The threshold enhancement effect in the dibaryon invariant mass and the angular distributions in the dibaryon rest frame are stressed and explained. Weak radiative baryonic B decays mediated by the electromagnetic penguin process $b\to sγ$ are discussed. Puzzles with the correlation observed in $B^-\to p\bar pK^-$ decay and the unexpectedly large rate observed for $B\toΛ_c\barΛ_cK$ are examined. The former may indicate that the $p\bar p$ system is produced through some intermediate states, while the latter implies t…
Baryon-to-meson and baryon-to-photon transition distribution amplitudes (TDAs) arise in the collinear factorized description of a class of hard exclusive reactions characterized by the exchange of a non-zero baryon number in the cross channel. These TDAs extend the concepts of generalized parton distributions (GPDs) and baryon distribution amplitudes (DAs). In this review, we discuss the general properties and physical interpretation of baryon-to-meson and baryon-to-photon TDAs. We argue that these non-perturbative objects are a convenient complementary tool to explore the structure of baryons…
We study the exclusive leptonic and semileptonic $B$ decays $B \to \ell^- \barν$ and $B \to D^{(\ast)} \ell^-\barν$ in the framework of the covariant quark model with built-in infrared confinement. We compute the relevant form factors in the full kinematical momentum transfer region. The calculated form factors are used to evaluate branching fractions and polarization observables of the above transitions. We compare our results with experimental data and results from other theoretical studies.
We study a set of exclusive $B$ and $B_s$ decay modes induced by the rare $b \to s ν\bar ν$ transition in the RS$_c$ model, an extra-dimensional extension of the standard model with warped 5D metric and extended gauge group. We emphasize the role of correlations among the observables, and their importance for detecting the predicted small deviations from the standard model expectations.
We use the exclusive baryonic $B$ decays to determine the Cabibbo-Kobayashi-Maskawa (CKM) matrix element $V_{ub}$. From the relation $|V_{ub}|^2/|V_{cb}|^2=({\cal B}_π/{\cal B}_D){\cal R}_{ff}$ based on $B^-\to p\bar p π^-$ and $\bar B^0\to p\bar p D^0$ decays, where $|V_{cb}|$ and ${\cal B}_π/{\cal B}_D\equiv{\cal B}(B^-\to p\bar p π^-)/{\cal B}(\bar B^0\to p\bar p D^0)$ are the data input parameters, while ${\cal R}_{ff}$ is the one fixed by the $B\to p\bar p$ transition matrix elements, we find $|V_{ub}|=(3.48^{+0.87}_{-0.63}\pm 0.40\pm 0.07)\times 10^{-3}$ with the errors corresponding to …
We present the first observation of exclusive $e^+e^-$ production in hadron-hadron collisions, using $p\bar{p}$ collision data at \mbox{$\sqrt{s}=1.96$ TeV} taken by the Run II Collider Detector at Fermilab, and corresponding to an integrated luminosity of \mbox{532 pb$^{-1}$}. We require the absence of any particle signatures in the detector except for an electron and a positron candidate, each with transverse energy {$E_T>5$ GeV} and pseudorapidity {$|η|<2$}. With these criteria, 16 events are observed compared to a background expectation of {$1.9\pm0.3$} events. These events are consistent …
We set a preliminary 95% C.L. exclusion on the oscillation frequency of $B_s^0 - \bar{B_s^0}$ mixing using a sample of 400,000 hadronic $Z^0$ decays collected by the SLD experiment at the SLC during the 1996-98 run. In this analysis, $B_s^0$ mesons are partially reconstructed by combining a fully reconstructed $D_s$ with other $B_s^0$ decay tracks. The $D_s$ decays are reconstructed via the $ϕπ$ and $K^* K$ channels. The $b$-hadron flavor at production is determined by exploiting the large forward-backward asymmetry of polarized $Z^0 \to b \bar{b}$ decays as well as information from the hemisp…
We report preliminary results on the measurement of branching fractions of exclusive decays of neutral and charged B mesons into two-body final states containing a charmonium state and a light strange meson. The charmonium mesons considered are J/psi, psi(2S) and chic_c1, and the light mesons are either K or K*. We use a sample of about 124 million BBbar events collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center.
Inspired by a large decay branching ratio (BR) of $B^{+}\to f_{0}(980)K^{+}$ measured by Belle recently, we propose that a significant evidence of the component of $n\bar{n}=(u\bar{u}+d\bar{d})/\sqrt{2}$ in $f_{0}(980)$ could be demonstrated in exclusive $b\to c$ decays by the observation of $f_{0}(980)$ in the final states $\bar{B}\to D^{0(*)} π^{+} π^{-}(KK)$ and $\bar{B}\to J/Ψπ^{+} π^{-}(KK)$. We predict the BRs of $\bar{B}\to D^{0(*)} (J/Ψ) f_{0}(980)$ to be ${\cal {O}}(10^{-4})$ (${\cal {O}}(10^{-5})$) while the unknown wave functions of $D^{(*)0}$ ($J/Ψ$) are chosen to fit the observed …
We extend our studies of a new class of $2 \to 3$ exclusive processes using the collinear factorisation framework by considering the exclusive photoproduction of a $γ\,ρ$ pair, in the kinematics where the pair has a large invariant mass, {and the outgoing $ ρ$-meson has a sufficiently large transverse momentum to not resonate with the nucleon}. We cover the whole kinematical range from medium energies in fixed target experiments to very large energies of colliders, by considering the experimental conditions of JLab~12-GeV, COMPASS, future EIC and LHC (in ultra-peripheral collisions) cases. One…
A search for narrow Theta(1540)^+, a candidate for pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction p+C(N) \to Theta^+ \bar{K}^0 + C(N) on carbon nuclei or quasifree nucleons at E_{beam}=70 GeV (sqrt{s} = 11.5 GeV) studying nK^+, pK_S and pK_L decay channels of Theta(1540)^+ in four different final states of the Theta^+ \bar{K}^0 system. In order to assess the quality of the identification of the final states with neutron or K_L we reconstructed Lambda(1520)\to nK_S and phi\to K_LK_S decays in the calibration reactions p+C(N)\to Lambda(152…
We report measurements of branching fractions and charge asymmetries of exclusive decays of neutral and charged B mesons into two-body final states containing a charmonium state and a light strange meson. The charmonium mesons considered are J/Psi, Psi(2S) and Chi_c1, and the light meson is either K or K*. We use a sample of about 124 million BBbar events collected with the BABAR detector at the PEP-II storage ring at the Stanford Linear Accelerator Center.
We consider the time-dependent analysis of rare $B_d$ and $B_s$ decays mediated by $b\to s ν\bar ν$ transitions. The inclusion of time evolution allows us to construct novel observables with specific sensitivity to CP-odd phases in these processes. The sensitivity to CP violation of corresponding time-integrated measurements in presence of flavor-tagging is also explored. We provide precise predictions for these observables in the SM and explore their sensitivity to new CP-violating NP contributions at present and planned future $B$-physics experiments. As such, these observables provide uniqu…
We evaluate semileptonic decays of spin-1/2 and spin-3/2 doubly heavy $cb$ baryons. The decays are driven by a $c\to s,d$ transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil.
In an exclusive measurement of the reaction $γd \to K^+ K^- p n$, a narrow peak that can be attributed to an exotic baryon with strangeness $S=+1$ is seen in the $K^+n$ invariant mass spectrum. The peak is at $1.542\pm 0.005$ GeV/c$^2$ with a measured width of 0.021 GeV/c$^2$ FWHM, which is largely determined by experimental mass resolution. The statistical significance of the peak is $5.2 \pm 0.6 σ$. The mass and width of the observed peak are consistent with recent reports of a narrow $S=+1$ baryon by other experimental groups.
Using 8.5M B-anti-B events recorded by the BABAR detector the yield of inclusive J/psi, the branching ratios of psi(2S) and chi_C1 are presented. Combining the charmonium state with either a K+,KS, K*+ or K*0 exclusive B decays are reconstructed and their branching ratios determined. Using the fully reconstructed decays, both the B0 and B+ masses and their difference is measured. Finally the contributions of CP even and odd amplitudes in the decay B to J/psi K* are determined from an angular analysis.
We have studied extracting $|\vub/\vcb|$ by calculating the ratios ${\cal B}(\bar{B}^0\to D_s^{(*)-}(π^+,ρ^+))/{\cal B}(\bar{B}^0\to D_s^{(*)-}D^{(*)+})$ including penguin effects within the factorization assumption. The ratios involving $\bar{B}^0\to D_s^-D^{+}$ mode have considerable penguin corrections ($\sim 15%$ at the amplitude level), but those involving $\bar{B}^0\to D_s^-D^{*+}$ mode have relatively small penguin corrections. On the other hand, the $\bar{B}^0\to D_s^-D^{+}$ mode has smaller form-factor dependance. Therefore, these ratios complement each other in measuring $\vub/\vcb$.…
We report branching fraction measurements for exclusive decays of charged and neutral B mesons into two-body final states containing a charmonium meson. We use a sample of 22.72 +/- 0.36 million B anti-B events collected between October 1999 and October 2000 with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. The charmonium mesons considered here are J/psi, psi(2S), and chi_c1, and the light meson in the decay is either a K, K^*, or pi^0.
There seem to be recently an evidence for $C =$ -1 exchanges in $p p$ and $p \bar p$ elastic scattering at high energies. The analysis there is difficult as the two processes were not measured at the same (large) energies. Here we discuss three different exclusive processes given in the title as a possible source of information for odderon exchange. A sketch of the formalism is presented for each of the reactions. We consider low energy processes measured in the past by the WA102 collaboration and try to make predictions for the LHC. We discuss possible evidences at the low energies and try to…
We present a study of three B0 decay modes useful for time-dependent CP asymmetry measurements. From a sample of 9.7 million B meson pairs collected with the CLEO detector, we have reconstructed B0 -> J/psi K0S, B0 -> chi_c1 K0S, and B0 -> J/psi pi0 decays. The latter two decay modes have been observed for the first time. We describe a K0S -> pi0 pi0 detection technique and its application to the reconstruction of the decay B0 -> J/psi K0S. Combining the results obtained using K0S -> pi+ pi- and K0S -> pi0 pi0 decays, we determine Br(B0 -> J/psi K0) = (9.5 +- 0.8 +- 0.6)*10^-4, where the first…
We propose to utilize the exclusive $Z$-boson rare decays $Z\to Υ(ns)+γ$ to constrain the $Zb\bar{b}$ couplings at the HL-LHC and 100 TeV proton-proton collider. We demonstrate that the event yield of the proposed processes is sensitive to the axial-vector component of the $Zb\bar{b}$ coupling and can provide complementary information to the jet-charge weighted single-spin asymmetry measurement at the EIC and the $gg\to Zh$ production rate measurement at the LHC. By applying the NRQCD factorization formalism, we calculate the partial decay width of $Z\to Υ(ns)+γ$ to the NLO accuracy in strong …
In the last years, the need of the colour octet state in inclusive P-wave charmonium decay has been firmly established. However, the implications of this in the corresponding exclusive reactions have not been fully recognized. We argue for the necessity of the colour octet in P- and higher-wave quarkonium decay. Using a set of phenomenologically constructed baryon wavefunctions, we consider the Chi_J decay into octet and decuplet baryon-antibaryon pair. By doing so, we subject the wavefunctions to a test of applicability. We show that the colour singlet component alone is insufficient to accou…
Exclusive rare Higgs decays into lepton pair plus one light hadron, such as $h\to ρ^0(ω)\ell\bar{\ell}$, $h\to π^0\ell\bar{\ell}$, $h\to π^+ (K^+)\ell^-\barν_\ell$, and $h\to ρ^+(K^{*+})\ell^-\barν_\ell$, have been explored in the standard model. Decay amplitudes are dominantly from the Higgs couplings to gauge bosons and to charged leptons, and their branching ratios are predicted in the range of $10^{-8}\sim 10^{-5}$. We have also analyzed the differential dilepton invariant mass and angular distributions of $h\to ρ^0 \ell^+\ell^-$ decays. It will be challenging to search for these rare proc…
The LHCb experiment has measured CP violation (CPV) across the Dalitz plot of charmless decays of B+ mesons to 3 charged tracks, namely in Kππ, KKK, πππ and πKK final states, with strikingly large CPV that vary strongly with Dalitz variables. Identifying these processes with b -> sqq(bar), sss(bar) and b -> dqq(bar), dss(bar), where q = u, d, then the "sum rule" that requires two-loop absorptive parts by unitarity works well for inclusive b -> s CPV, but less well for inclusive b -> d case. We elucidate the situation, and argue that the 30 year old unitarity/CPT argument is valid to this day, …
Production of $f_0(1710)$, a theoretical endeavor of pure scalar glueball state, is studied in detail from exclusive rare B decay within the framework of perturbative QCD. The branching fraction for $B^\pm \to K^{*\pm} f_0(1710) \to K^{*\pm} (K \bar K)$ is estimated to be about $8 \times 10^{-6}$, while for $B^\pm \to K^\pm f_0(1710) \to K^\pm (K \bar K)$ it is smaller by roughly an order of magnitude. With the accumulation of almost 1 billion $B \bar B$ pairs from the B{\tiny A}B{\tiny AR} and Belle experiments to date, hunting for a scalar glueball via these rare decay modes should be attain…
Accessing chiral-even quark generalised parton distributions in the exclusive photoproduction of a $ γπ^{\pm} $ pair with large invariant mass in both fixed-target and collider experiments
The processes of exclusive diffractive scattering $p+p\to p+p$, $\bar p+p\to\bar p+p$, and $γ^*+p\to V+p$ at high energies are considered in the framework of a unified Regge-eikonal model with a very simple reggeon structure of the eikonal. It is demonstrated that the pomeron trajectory is universal in all reactions and having intercept about 1.31 which could be exctracted explicitly from the data on the proton structure function $F_2(x,Q^2)$. The predictions for the proton-proton cross-sections at LHC energies are given.
We perform a model-independent fit of the short-distance couplings $C_{7,9,10}$ within the Standard Model set of $b\to sγ$ and $b\to s\bar\ell\ell$ operators. Our analysis of $B \to K^* γ$, $B \to K^{(*)} \bar\ell\ell$ and $B_s \to \barμμ$ decays is the first to harness the full power of the Bayesian approach: all major sources of theory uncertainty explicitly enter as nuisance parameters. Exploiting the latest measurements, the fit reveals a flipped-sign solution in addition to a Standard-Model-like solution for the couplings $C_i$. Each solution contains about half of the posterior probabili…
We present a systematical study of two-body and three-body charmless baryonic B decays. Branching ratios for two-body modes are in general very small, typically less than $10^{-6}$, except that $\B(B^-\to p \barΔ^{--})\sim 1\times 10^{-6}$. In general, $\bar B\to N\barΔ>\bar B\to N\bar N$ due to the large coupling constant for $Σ_b\to BΔ$. For three-body modes we focus on octet baryon final states. The leading three-dominated modes are $\bar B^0\to p\bar nπ^-(ρ^-), n\bar pπ^+(ρ^+)$ with a branching ratio of order $3\times 10^{-6}$ for $\bar B^0\to p\bar nπ^-$ and $8\times 10^{-6}$ for $\bar B^…
Flavor SU(3) symmetry is a powerful tool to analyze charmed baryon decays, however its applicability remains to be experimentally validated. Since there is not much data on $Ξ_c$ decays, various exclusive $Λ_c$ decays especially the ones into a neutron state are essential for the test of flavor symmetry. These decay modes are also helpful to investigate final state interactions in charmed baryon decays. In this work, we discuss the explicit roles of $Λ_c$ decays into a neutron in testing the flavor symmetry and exploring final state interactions. The involved decay modes include semileptonic d…
The elastic production of top quark pairs in $pp$ collisions at low and high luminosity regimes is investigated in detail. We extend the study performed in Phys. Rev. D102, 074014 (2020) which has demonstrated that the sum of two semi-exclusive $t\bar{t}$ production modes, namely in photon-Pomeron and Pomeron-Pomeron interactions, can be experimentally measured when the $t\bar{t}$ system decays semi-leptonically, $t\bar{t}\rightarrow jjblν_l\bar{b}$, both forward protons are tagged and a low amount of pile-up is present. In this study we focus on separating individual channels and a special at…
We have fully reconstructed decays of both B0 and B- Mesons into final states containing either D, D*, D**, Psi, Psi', or Chi_{c1} mesons. This allows us to obtain new results on many physics topics including branching ratios, tests of the factorization hypothesis, color suppression, resonant substructure, and the B- - B0 mass difference.
We study the four-body exclusive semileptonic baryonic $\bar B$ decays of $B^-\to p\bar p \ell^- \barν_{\ell}$ ($\ell=e,μ,τ$) in the standard model. We find that their decay branching ratios are about $(1.0, 1.0,0.5)\times 10^{-4}$, respectively. In particular, the electron mode is close to the corresponding CLEO's upper limit of $5.2\times 10^{-3}$, while all results are about one or two orders of magnitude larger than the previous estimated values for the inclusive modes of $\bar B\to {\bf B\bar B'}\ell \bar ν$. Clearly, both B-factories of Belle and BaBar should be able to observe these exc…
We consider central exclusive diffractive dipion production in the reactions $pp \to pp π^{+} π^{-}$ and $p\bar{p} \to p\bar{p} π^{+} π^{-}$ at high energies. We include the dipion continuum, the dominant scalar $f_{0}(500)$, $f_{0}(980)$, and tensor $f_{2}(1270)$ resonances decaying into the $π^{+} π^{-}$ pairs. The calculation is based on a tensor pomeron model and the amplitudes for the processes are formulated in terms of vertices respecting the standard crossing and charge-conjugation relations of Quantum Field Theory. The formulae for the dipion continuum and tensor meson production are …
We study the exclusive photoproduction of a photon-meson pair with a large invariant mass, working in the QCD factorisation framework. Explicitly, we consider a $ ρ$-meson or a charged $ π$ in the final state. This process gives access to chiral-even GPDs as well as chiral-odd GPDs. We focus here on the chiral-even sector. The computation is performed at leading order and leading twist. We discuss the prospects of measuring them in various experiments such as JLab 12-GeV, COMPASS, future EIC and LHC (in ultraperipheral collisions). In particular, the high centre of mass energies available at c…
In inclusive P-wave charmonium decay, to cancel infrared divergence in the colour singlet contribution requires the inclusion of the colour octet which becomes degenerate with the former in the infrared limit. In the corresponding exclusive decay, such an infrared divergence does not exist. On this ground, it becomes doubtful whether the colour octet is needed in exclusive reactions. A contradiction in the underlying picture, however, would result once all strong decay channels are summed. We provide an answer to this question in support of the colour octet with theoretical arguments as well a…
We extract the Cabibbo-Kobayashi-Maskawa matrix element $V_{cb}$ from the exclusive decays of $Λ_b\to Λ_c\ell\bar ν_\ell$ and $Λ_b\to Λ_c M_{(c)}$ with $M=(π^-,K^-)$ and $M_c=(D^-,D^-_s)$, where the branching ratios of $Λ_b\to ΛM_{(c)}$ measured with high precisions have not been used in the previous studies. Explicitly, we find $|V_{cb}|=(44.0\pm 3.5)\times 10^{-3}$, which agrees with the value of $(42.11\pm 0.74)\times 10^{-3}$ from the inclusive $B\to X_c\ell\bar ν_\ell$ decays. Furthermore, based on the most recent ratio of $|V_{ub}|/|V_{cb}|$ from the exclusive $Λ_b$ decays, we obtain $|V…
