Very recent experimental information obtained from the Belle experiment, along with that accumulated by the BABAR and LHCb experiments, has shown the existence of anomalies in the ratios R(D) and ...R(D*) associated with the charged-current transition b→cτντ. Although the Belle measurements are in agreement with standard model (SM) predictions, the new experimental world averages still exhibit a tension. In addition, the D* longitudinal polarization FL(D*) related with the channel B→D*τντ observed by the Belle Collaboration and the ratio R(J/ψ) measured by the LHCb Collaboration also show discrepancies with their corresponding SM estimations. We present a model-independent study based on the most general effective Lagrangian that yields a tree-level effective contribution to the transition b→cτντ induced by a general W′ boson. Instead of considering any specific new physics (NP) realization, we perform an analysis by considering all of the different chiral charges to the charm-bottom and τ−ντ interaction terms with a charged W′ boson that explain the anomalies. We present a phenomenological study of parameter space allowed by the new experimental b→cτντ data and with the mono-tau signature pp→τhX+MET at the LHC. For comparison, we include some of the W′ boson NP realizations that have already been studied in the literature.
Structure in the di-J/ψ mass spectrum observed by the LHCb experiment around 6.9 and 7.2 GeV is interpreted in terms of JPC = 0++ and 2++ resonances between a cc diquark and a ¯c¯c antidiquark, using ...a recently confirmed string-junction picture to calculate tetraquark masses. The main peak around 6.9 GeV is likely dominated by the 0++ (2S) state, a radial excitation of the cc−¯c¯c tetraquark, which we predict at 6.871 ± 0.025 GeV. The dip around 6.75 GeV is ascribed to the opening of the S-wave di-χc0 channel, while the dip around 7.2 GeV could be correlated with the opening of the di-ηc(2S) or Ξcc¯Ξcc channel. The low-mass part of the di-J/ψ structure appears to require a broad resonance consistent with a predicted 2++ (1S) state with invariant mass around Minv = 6400 MeV. Implications for bb¯b¯b tetraquarks are discussed.
We present the new parton distribution functions (PDFs) from the CTEQ-TEA collaboration, obtained using a wide variety of high-precision Large Hadron Collider (LHC) data, in addition to the combined ...HERA I + II deep-inelastic scattering dataset, along with the datasets present in the CT14 global QCD analysis. New LHC measurements in single-inclusive jet production with the full rapidity coverage, as well as production of Drell-Yan pairs, top-quark pairs, and high-pT Z bosons, are included to achieve the greatest sensitivity to the PDFs. The parton distributions are determined at next-to-leading order and next-to-next-to-leading order, with each of these PDFs accompanied by error sets determined using the Hessian method. Fast PDF survey techniques, based on the Hessian representation and the Lagrange multiplier method, are used to quantify the preference of each data set to quantities such as αs(mZ), and the gluon and strange quark distributions. We designate the main resulting PDF set as CT18. The ATLAS 7 TeV precision W / Z data are not included in CT18, due to their tension with other datasets in the global fit. Alternate PDF sets are generated including the ATLAS precision 7 TeV W / Z data (CT18A), a new scale choice for low- x DIS data (CT18X), or all of the above with a slightly higher choice for the charm mass (CT18Z). Theoretical calculations of standard candle cross sections at the LHC (such as the g g fusion Higgs boson cross section) are presented.
Recently, the LHCb Collaboration reported pronounced structures in the invariant mass spectrum of J/ψ pairs produced in proton-proton collisions at the Large Hadron Collider. In this Letter, we argue ...that the data can be very well described within two variants of a coupled-channel approach employing T matrices consistent with unitarity: (i) with just two channels, J/ψJ/ψ and ψ(2S)J/ψ, as long as energy-dependent interactions in these channels are allowed, or (ii) with three channels J/ψJ/ψ, ψ(2S)J/ψ, and ψ(3770)J/ψ with just constant contact interactions. Both formulations hint at the existence of a near-threshold state in the J/ψJ/ψ system with the quantum numbers J^{PC}=0^{++} or 2^{++}, which we refer to as X(6200). We suggest experimental tests to check the existence of this state and discuss what additional channels need to be studied experimentally to allow for distinctive tests between the two mechanisms proposed. If the molecular nature of X(6200), as hinted by the three-channel approach, is confirmed, many other double-quarkonium states should exist driven by the same binding mechanism. In particular, there should be an η_{c}η_{c} molecule with a similar binding energy.
We demonstrate that four top-quark production is a powerful tool to constrain the top Yukawa coupling. The constraint is robust in the sense that it does not rely on the Higgs boson decay. Taking ...into account the projection of the tt¯H production by the ATLAS Collaboration, we obtained a bound on the Higgs boson width, ΓH≤2.57ΓHSM, at the 14 TeV Large Hadron Collider with an integrated luminosity of 300 fb−1.
Zusammenfassung
Zurzeit ist die Flavour‐Physik mit der Untersuchung von Zerfällen von B‐Mesonen ein interessanter Bereich der experimentellen Teilchenphysik, da sie wichtige Tests des Standardmodells ...ermöglicht. Das kürzlich überarbeitete LHCb‐Experiment wurde neu gestartet und soll eine bisher unerreichte Präzision in der Vermessung der Eigenschaften der B‐Mesonen liefern.
Abstract
Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively
1,2
. Here, we report the observation of a hadronic state ...containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a
$$\overline{{{u}}}$$
u
¯
and a
$$\overline{{{d}}}$$
d
¯
quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of
D
0
D
0
π
+
mesons just below the
D
*+
D
0
mass threshold. The near-threshold mass together with the narrow width reveals the resonance nature of the state.
Mesons comprising a beauty quark and strange quark can oscillate between particle (Bs0) and antiparticle (B¯s0) flavour eigenstates, with a frequency given by the mass difference between heavy and ...light mass eigenstates, Δms. Here we present a measurement of Δms using Bs0→Ds−π+ decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δms = 17.7683 ± 0.0051 ± 0.0032 ps−1, where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δms precision by a factor of two. We combine this result with previous LHCb measurements to determine Δms = 17.7656 ± 0.0057 ps−1, which is the legacy measurement of the original LHCb detector.The LHCb collaboration reports an improved measurement of the oscillation frequency of mesons consisting of a bottom quark and strange quark, which is then combined with previous results.
In this paper we investigate the inclusive associated production of ϒ + γ at hadron colliders. We calculate the color-singlet subprocesses and all three color-octet subprocesses at the ...next-to-leading order. Seven sets of long distance matrix elements (LDMEs), which are extracted from the studies on the prompt production of ϒ at hadron colliders, are used to give the numerical results and we find that there are three sets of LDMEs giving the unphysical results on the yield and the polarization for this process. The yield could be enhanced by several times or even two orders of magnitude compared to the color-singlet contribution and the polarization changes from longitudinal to slightly transverse or even mainly transverse in the large pt region. The estimated results indicate that to study the process at the Large Hadron Collider (LHC) is difficult and it may be well investigated at the future Super Proton-Proton Collider (SPPC).
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