YSF Measurement of the shape of the $\mathrm{b}$ quark fragmentation function using charmed mesons produced inside $\mathrm{b}$ jets from $\mathrm{t\overline{t}}$ decays
A first measurement of the $\mathrm{b}$ quark fragmentation function at the LHC is presented. Charmed meson candidates produced via semi-leptonic $\mathrm{t\overline{t}}$ decays ($\mathrm{t} \to \mathrm{b}\mathrm{W} \to$ b-jet $\ell ν$) are used as a proxy for the parent $\mathrm{B}$ meson. Templates are generated at various values of the fragmentation shape parameter $r_{\mathrm{b}}$, and are fit to the data to measure the value of $r_{\mathrm{b}}$. The final fit result is $r_{\mathrm{b}}=0.855 \pm 0.037\;\mathrm{(stat)} \pm 0.031\;\mathrm{(syst)}$. This is the first measurement of the $\mathrm{b}$ quark fragmentation function within a color rich environment, and is consistent with previous results from $e^+e^-$ colliders.
The lifetimes of charmed mesons have been measured using 11.1fb$^{-1} of data collected with the Belle detector at KEKB. Each candidate is fully reconstructed to identify the flavor of the charmed meson. The lifetimes are measured to be $τ(D^0)=(414.5\pm1.7)$ fs, $τ(D^+)=(1029\pm12)$ fs and $τ(D_s^+)=(488.4^{+7.8}_{-7.7})$ fs, where the error is statistical only. The mixing parameter $y_{CP}$ is also measured to be $y_{CP}=(1.16^{+1.67}_{-1.65}(stat.))%$ through the lifetime difference of $D^0$ mesons decaying into CP-mixed states and CP eigenstates.
The mid-rapidity transverse-momentum spectra of charmed meson in Pb-Pb and pp($\overline{\text{p}}$) collisions are analyzed by Tsallis-Pareto distribution derived from non-extensive statistics. We perform uniform descriptions for both small and large systems over a wide range of collision energy and hadron transverse momentum. By establishing the relation between the event multiplicity and the Tsallis parameters, we observe that there is significant linearity between thermal temperature and Tsallis-q parameter in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV and 5.02 TeV. And the slope of th…
The strong decays of the pseudoscalar and scalar double-charmed tetraquarks $ T_{cc;\overline{u}\overline{d}}^{+}$ and $\widetilde{T}_{cc;\overline{u} \overline{d}}^{+}$ are investigated in the framework of the QCD sum rule method. The mass and coupling of these exotic four-quark mesons are calculated in the framework of the QCD two-point sum rule approach by taking into account vacuum condensates of the quark, gluon, and mixed local operators up to dimension 10. Our results for masses $m_{T}=(4130~\pm 170)~ \mathrm{MeV} $ and $m_{\widetilde{T}}=(3845~\pm 175)~\mathrm{MeV}$ demonstrate that th…
The vast amount of $c\overline{c}$ production that can be recorded by the LHCb detector makes it an ideal environment to study the hadronic production of charmed baryons, along with the properties of their decays. We briefly describe the LHCb experiment and the triggering mechanisms it uses for recording charm production. Previous charmed baryon results from LHCb are detailed, with a description of the future plans for the charmed baryon programme.
We study the properties of charmed, nonstrange, $\rm D$ mesons produced in continuum $\rm {e^+}{e^-}$ annihilations. The $ \rm {e^+}{e^-}$ collisions were generated in the energy region of the $ \rm Υ(3S)$ and $ \rm Υ(4S)$ resonances by the Cornell Electron Storage Ring, and were analyzed by the CLEO detector. We make extensive study of the decay topology $\rm D^0, D^+ \rightarrow \overline{\rm K}^{_{_0}}X$, where the $\overline{\rm K}^{_{_0}}$ is observed in the final state $\rm K^{0}_{S} \rightarrow π^+π^-$. The decay $ \rm D^+ \rightarrow K^- π^+π^-$ is also considered. We analyze the hadro…
In this work, we treat the newly observed doubly charmed four-quark state $ T_{cc}^{+}$ as an axial-vector tetraquark with content $cc\overline{u} \overline{d}$, and calculate its spectroscopic parameters and width. The mass and current coupling of the tetraquark $T_{cc}^{+}$ are found by means of the QCD two-point sum rule method by taking into account quark, gluon and mixed condensates up to dimension $10$. The width of the $T_{cc}^{+}$ is evaluated using partial widths of decay processes $T_{cc}^{+} \to \widetilde{ T}π^{0}$ and $T_{cc}^{+} \to T_{cc;\overline{u}\overline{u}}^{0}π^{+}$ , whe…
We investigate a nonrelativistic model of tetraquarks, which are assumed to be compact and to consist of diquark-antidiquark pairs. We fit, for the first time, basically all currently known values for the measured masses of 45 mesons, including both charmed and bottom mesons, to the model and predict masses of tetraquarks as well as diquarks. In particular, we find masses of four axial-vector diquarks, i.e., $qc$, $cc$, $qb$, and $bb$, where $q = u,d$, and 24 ground-state tetraquarks, including both heavy-light tetraquarks ($qc\overline{qc}$ and $qb\overline{qb}$) and heavy tetraquarks ($cc\ov…
In the present work, we study the production problem of the charmed baryon $Λ_c(2860)^+$ at $\overline{\mbox{P}}$ANDA. With the $J^P=\frac{3}{2}^+$ assignment to $Λ_c(2860)^+$, an effective Lagrangian approach is adopted to calculate the cross section of $p\bar{p} \to Λ_c^-Λ_c(2860)^+$. The Dalitz plot analysis and the $D^0p$ invariant mass spectrum distribution are also given for the $p\bar{p} \to Λ_c^-Λ_c(2860)^+ \to Λ_c^-pD^0$ process. The numerical results show that the total cross section may reach up to about 10 $ μ$b. With the designed luminosity of $\overline{\mbox{P}}$ANDA ($2\times10…
The mass, decay constant and width of a hypothetical charmed partner $X_c$ of the newly observed exotic $X_b(5568)$ state are calculated using a technique of QCD sum rule method. The $X_c=[su][\overline{c}\overline{d}]$ state with $J^{P}=0^{+}$ is described employing two types of the diquark-antidiquark interpolating currents. The evaluation of the mass $m_{X_c}$ and decay constant $f_{X_c}$ is carried out utilizing the two-point sum rule method by including vacuum condensates up to eight dimensions. The widths of the decay channels $X_c \to D_s^{-} π^{+}$ and $X_c \to D^{0} K^{0}$ are also fo…
Two-body hadronic weak decays of the charmed baryon $Ω_c$, including Cabibbo-favored (CF), singly Cabibbo-suppressed (SCS) and doubly Cabibbo-suppressed (DCS) modes, are studied systematically in this work. To estimate nonfactorizable contributions, we work in the pole model for the $P$-wave amplitudes and current algebra for the $S$-wave amplitudes. Among all the channels decaying into a baryon octet and a pseudoscalar meson, $Ω_c\to Ξ^0\overline{K}^0$ is the only allowed CF mode. The predicted branching fraction of order $3.8\%$ and large and positive decay asymmetry of order $0.50$ indicate…
Hadronic states composed of multi-quark flavors may exist in reality since they are not prohibited by QCD. Compact four quark systems of color singlet are classified as tetraquarks. To understand the properties of these states, more theoretical and experimental efforts are needed. In this work, we study charmed tetraquarks with three light flavors using flavor $SU(3)$ symmetry. States with three different light quarks must be in a ${\bf \bar 6 }$ or a ${\bf 15}$ multiplet. We investigate the production of charmed tetraquarks $X_c$ in $B\to X_c (\overline {X}_c) P$ and $B_c \to X_c P$ decays. W…
We analyze the decay processes of ${\bf B}_c \to {\bf B}_n M$ with the $SU(3)_F$ flavor symmetry and spin-dependent amplitudes, where ${\bf B}_c({\bf B}_n)$ and $M$ are the anti-triplet charmed (octet) baryon and nonet meson states, respectively. In the $SU(3)_F$ approach, it is the first time that the decay rates and up-down asymmetries are fully and systematically studied without neglecting the ${\cal O}(\overline{15})$ contributions of the color anti-symmetric parts in the effective Hamiltonian. Our results of the up-down asymmetries based on $SU(3)_F$ are quite different from the previous …
The main aim of this paper is to present new sets of non-perturbative fragmentation functions (FFs) for $D^0$ and $D^+$ mesons at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the $\overline{\mathrm{MS}}$ factorization scheme with five massless quark flavors. This new determination of FFs is based on the QCD fit to the {\tt OPAL} experimental data for hadron production in the electron-positron single-inclusive annihilation (SIA). We discuss in detail the novel aspects of the methodology used in our analysis and the validity of obtained FFs by compari…
Measurement of the Ratio of Partial Branching Fractions of Inclusive $\overline{B} \to X_u \ell \overlineν$ to $\overline{B} \to X_{c} \ell \overlineν$ and the Ratio of their Spectra with Hadronic Tagging
The hadronic two-body weak decays of the doubly charmed baryons $Ξ_{cc}^{++}, Ξ_{cc}^+$ and $Ω_{cc}^+$ are studied in this work. To estimate the nonfactorizable contributions, we work in the pole model for the $P$-wave amplitudes and current algebra for $S$-wave ones. For the $Ξ_{cc}^{++}\to Ξ_c^+π^+$ mode, we find a large destructive interference between factorizable and nonfactorizable contributions for both $S$- and $P$-wave amplitudes. Our prediction of $\sim 0.70\%$ for its branching fraction is smaller than the earlier estimates in which nonfactorizable effects were not considered, but a…
The production cross sections of the prompt charmed mesons ${\rm D^0}$, ${\rm D^+}$, ${\rm D^{*+}}$ and ${\rm D_s^+}$ were measured at mid-rapidity in proton-proton collisions at a centre-of-mass energy $\sqrt{s}=7$ TeV with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays ${\rm D}^0 \to {\rm K}^-π^+$, ${\rm D}^+\to {\rm K}^-π^+π^+$, ${\rm D}^{*+} \to {\rm D}^0 π^+$, ${\rm D_s^{+}\to ϕπ^+\to K^-K^+π^+}$, and their charge conjugates. With respect to previous measurements in the same rapidity region, the coverage in transverse momentum ($p_{\rm…
Studies of $e^+e^- \to D_s^+ \overline{D}{}^{(*)0}K^-$ and the $P$-wave charmed-strange mesons are performed based on an $e^+e^-$ collision data sample corresponding to an integrated luminosity of 567 pb$^{-1}$ collected with the BESIII detector at $\sqrt{s}= 4.600$ GeV. The processes of $e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-$ and $D_s^+ \overline{D}{}^{0} K^-$ are observed for the first time and are found to be dominated by the modes $D_s^+ D_{s1}(2536)^-$ and $D_s^+ D^*_{s2}(2573)^-$, respectively. The Born cross sections are measured to be $σ^{B}(e^+e^-\to D_s^+ \overline{D}{*}^{0} K^-) =…
First observation of the $\overline{B}_{s}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$ decay and evidence for the $\overline{B}^{0}\toΛ_{c}^{+}\overlineΛ_{c}{}^{-}$ decay
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究组织（CERN））
The decay of the narrow resonance $\overline{B}{}_{s2}^{*0}\!\rightarrow B^- K^+$ can be used to determine the $B^-$ momentum in partially reconstructed decays without any assumptions on the decay products of the $B^-$ meson. This technique is employed for the first time to distinguish contributions from $D^0$, $D^{*0}$, and higher-mass charmed states ($D^{**0}$) in semileptonic $B^-$ decays by using the missing-mass distribution. The measurement is performed using a data sample corresponding to an integrated luminosity of 3.0 fb${}^{-1}$ collected with the LHCb detector in $pp$ collisions at …
We calculate in three-flavor lattice QCD the short-distance hadronic matrix elements of all five $ΔC=2$ four-fermion operators that contribute to neutral $D$-meson mixing both in and beyond the Standard Model. We use the MILC Collaboration's $N_f = 2+1$ lattice gauge-field configurations generated with asqtad-improved staggered sea quarks. We also employ the asqtad action for the valence light quarks and use the clover action with the Fermilab interpretation for the charm quark. We analyze a large set of ensembles with pions as light as $M_π\approx 180$ MeV and lattice spacings as fine as $a\a…
