We have systematically calculated the mass spectra for S-wave and P-wave fully-charm $cbar{c}cbar{c}$ and fully-bottom $bbar{b}bbar{b}$ tetraquark states in the $mathbf{8}_{[Qbar{Q}]}otimes mathbf{8}_{[Qbar{Q}]}$ color configuration, by using the mom
ent QCD sum rule method. The masses for the fully-charm $cbar ccbar c$ tetraquark states are predicted about $6.3-6.5$ GeV for S-wave channels and $7.0-7.2$ GeV for P-wave channels. These results suggest the possibility that there are some $mathbf{8}_{[cbar{c}]}otimes mathbf{8}_{[cbar{c}]}$ components in LHCbs di-$J/psi$ structures. For the fully-bottom $bbar{b}bbar{b}$ system, their masses are calculated around 18.2 GeV for S-wave tetraquark states while 18.4-18.6 GeV for P-wave ones, which are below the $eta_beta_b$ and $Upsilon(1S)Upsilon(1S)$ two-meson decay thresholds.
The fraction of $Z+$jet events that contain a charm jet is measured for the first time in the forward region of proton-proton collisions. The data sample used corresponds to an integrated luminosity of 6 fb$^{-1}$ collected at a center-of-mass energy
of $13$ TeV with the LHCb detector. The ratio of production cross sections ${sigma(Zc)/sigma(Zj)}$ is determined in intervals of $Z$-boson rapidity in the range $2.0 < y(Z) < 4.5$. A sizable enhancement is observed in the forward-most $y(Z)$ interval, which could be indicative of a valence-like intrinsic-charm component in the proton wave function.
We review heavy quark flavor and spin symmetries, their exploitation in heavy meson effective theories and the flavored couplings of charmed and light mesons in the definition of their effective Lagrangians. We point out how nonperturbative continuum
QCD approaches based on Dyson-Schwinger and Bethe-Salpeter equations can be used to calculate strong and leptonic decays of open-charm mesons and heavy quarkonia. The strong decay $D^*to Dpi$ serves as a benchmark, as it is the only physical open-charm observable that can be related to the effective Lagrangians couplings. Nonetheless, a quantitative comparison of $D^*Dpi$, $rho DD$, $rho D^*D$ and $rho D^* D^*$ couplings for a range of off-shell momenta of the $rho$-meson invalidates SU(4)$_F$ symmetry relations between these couplings. Thus, besides the breaking of flavor symmetry by mass terms in the Lagrangians, the flavor-symmetry breaching in couplings and their dependence on the $rho$-meson virtuality cannot be ignored. We also take the opportunity to present new results for the effective $J/psi DD$ and $J/psi D^*D$ couplings. We conclude this contribution with a discussion on how the description of pseudoscalar and vector $D$, $D_s$, $B$ and $B_s$ meson properties can be drastically improved with a modest modification of the flavor-dependence in the Bethe-Salpeter equation.
The Large Hadron-Electron Collider (LHeC) will operate at $sqrt{s}$ = 1.2 TeV and accumulate about 1/ab of integrated electron-proton luminosity. Novel studies of high energy photon-photon interactions at the LHeC, at the $gammagamma$ center-of-mass
energy up to 1 TeV, will open new frontiers in the electroweak physics as well as in searches for physics beyond the Standard Model. Despite a very high $ep$ luminosity, the experimental conditions will be very favorable at the LHeC - a negligible event pileup will allow for unique studies of a number of processes involving the exclusive production via photon-photon fusion.
Heavy quarks (charm and beauty) are produced in hard-scattering processes and the study of their production in proton--proton (pp) collisions is an important test for calculations based on perturbative Quantum Chromodynamics (pQCD). Heavy-flavor prod
uction as a function of charged-particle multiplicity provides insight into the processes occurring at the partonic level and the interplay between the hard and soft particle production mechanisms in pp collisions. In this contribution, measurements of open heavy-flavor production as a function of multiplicity, via the study of the $mathrm{D}$-meson self-normalized yields in pp collisions at the center-of-mass energy of $sqrt{s} = 13$ TeV is presented. The $mathrm{D}$-meson self-normalized yield is found to increase stronger than linearly with increasing charged-particle multiplicity. The measurements are compared to theoretical model calculations, and with the results at $sqrt{s} = 7$ TeV.
We show in this work how a sub-100 GeV $Z$ in a $U(1)$ extension of the Standard Model (SM) can emerge through Higgs mediated channels at the Large Hadron Collider (LHC). The light $Z$ has minimal interaction with the SM sector as well as vanishing k
inetic mixing with $Z$ boson which allows it to be light and below the SM gauge boson masses. Interestingly such a light $Z$ is very difficult to observe in the standard production modes. We show that it is possible to observe such a gauge boson via scalar mediators that are responsible for the symmetry breaking mechanism of the model. The model also provides a dark matter candidate whose compatibility with the observed relic density is established due to the light $Z$. We also comment on other interesting possibilities such a light $Z$ may present for other observables.
Proton-proton ($pp$) collision has been considered as a baseline to study the system produced in relativistic heavy-ion (AA) collisions with the basic assumption that no thermal medium is formed in $pp$ collisions. This warrants a cautious analysis o
f the system produced in $pp$ collisions at relativistic energies.In this work we investigate the charmonium suppression in $pp$ collisions at $sqrt{s} = 7$ and $13$ TeV to inspect the system formed in these collisions. In this work, charmonium suppression has been studied for various event multiplicities and transverse momenta by including the mechanisms of color screening, gluonic dissociation, collisional damping along with the regeneration due to correlated $cbar c$ pairs. Here we obtain a net suppression of charmonia at high-multiplicity events indicating the possibility towards the formation of quark-gluon plasma in $pp$ collisions.
We propose a novel method for the elimination of negative Monte Carlo event weights. The method is process-agnostic, independent of any analysis, and preserves all physical observables. We demonstrate the overall performance and systematic improvemen
t with increasing event sample size, based on predictions for the production of a W boson with two jets calculated at next-to-leading order perturbation theory.
Hadron spectroscopy provides direct physical measurements that shed light on the non-perturbative behavior of quantum chromodynamics (QCD). In particular, various exotic hadrons such as the newly observed $T_{cc}^+$ by the LHCb collaboration, offer u
nique insights on the QCD dynamics in hadron structures. In this letter, we demonstrate how heavy ion collisions can serve as a powerful venue for hadron spectroscopy study of doubly charmed exotic hadrons by virtue of the extremely charm-rich environment created in such collisions. The yields of $T_{cc}^+$ as well as its potential isospin partners are computed within the molecular picture for Pb-Pb collisions at center-of-mass energy $2.76~mathrm{TeV}$. We find about three-order-of-magnitude enhancement in the production of $T_{cc}^+$ in Pb-Pb collisions as compared with the yield in proton-proton collisions, with a moderately smaller enhancement in the yields of the isospin partners $T_{cc}^0$ and $T_{cc}^{++}$. The $T_{cc}^+$ yield is comparable to that of the $X(3872)$ in the most central collisions while shows a considerably stronger decrease toward peripheral collisions, due to a threshold effect of the required double charm quarks for $T_{cc}^+$. Final results for their rapidity and transverse momentum $p_T$ dependence as well as the elliptic flow coefficient are reported and can be tested by future experimental measurements.
The BESIII experiment has collected the $e^+e^-$ collision data samples corresponding to integrated luminosities of 2.93 $mathrm{fb}^{-1}$, $3.19$ $mathrm{fb}^{-1}$, 3.13 $mathrm{fb}^{-1}$ and 567 $mathrm{pb}^{-1}$ at center-of-mass energies of 3.773
GeV, 4.178 GeV, 4.189-4.226 GeV and 4.599 GeV, respectively. We report the measurements of strong-phase parameters based on the decays $D^0to K^0_{S/L}pi^+pi^-$, $D^0to K^0_{S/L}K^+K^-$, $D^0to K^-pi^+pi^+pi^-$ and $D^0to K^-pi^+pi^0$, which are important input for binned model-independent measurement of the CKM angle $gamma/phi_3$. In addition, we report amplitude analyses and branching fraction measurements of $D^+$, $D_s^+$ and $Lambda_c^+$ decays along with the $Lambda_c^+$ spin determination.
