Heavy flavor productions are important tests of QCD. In proton-proton collisions collected at LHCb, a long list of measurements for charm and bottom productions have been made. This talk focuses on the studies of fragmentation functions and production asymmetries for bottom hadrons. They provide inputs for absolute branching fraction measurements and CP violation studies at LHCb respectively.
The electroweak sector of the Standard Model contains three generations of charged leptons $\ell^-\in\{e^-,μ^-,τ^-\}$ as exact replicas of each other, except for their Yukawa couplings to the Higgs that determine their masses. The Yukawas, and thereby, the masses, are not predicted but are parameters in the theory. A basic tenet in the formalism, known as lepton universality, is equality of the couplings to the electroweak gauge bosons $\{γ, Z, W^-\}$ among all three generations, and has mostly stood the test of time. However, precision tests in $B$ decays have recently posed serious challenge…
We propose a predictive radiative seesaw model at one-loop level with a flavor dependent gauge symmetry $U(1)_{xB_3-xe-μ+τ}$ and Majorana fermion dark matter. For the neutrino mass matrix, we obtain an $A_1$ type texture (with two zeros) that provides us several predictions such as the normal ordering for the neutrino masses. We analyze the constraints from lepton flavor violations, relic density of dark matter, and collider physics for the new $U(1)_{xB_3-xe-μ+τ}$ gauge boson. Within the allowed region, the LHCb anomalies in $B\rightarrow K^* μ^+ μ^-$ and $B\rightarrow K \ell^+ \ell^-$ with $…
We study an extended Standard Model with a gauged U(1)$^{\prime}$ flavor symmetry, motivated not only by the fermion mass hierarchy but also by the excesses in $B \to K^{(*)} l l$ reported by the LHCb collaborations. The U(1)$^{\prime}$ charges are assigned to quarks and leptons in a flavor-dependent manner, and flavored Higgs doublets are also introduced in order to detail the Yukawa couplings at the renormalizable level. Then, the fermion mass hierarchy is realized by the vacuum alignment of the Higgs doublets. In this model, flavor-changing currents involving the gauge boson of U(1)$^{\prim…
We quantify the constraints on the flavour separation between the quarks and antiquarks in the proton provided by the recent forward weak gauge boson production data from the LHCb experiment at $\sqrt{s}=7$ and 8 TeV. Performed in the framework of the NNPDF3.1 global analysis, this study highlights the key role that the LHCb W and Z data have in achieving a robust quark flavour separation in the large-x region, including the strange and charm quarks. We demonstrate how the LHCb measurements lead to improved determinations of the the up and down quark PDFs in the region $x\ge 0.1$, with an unce…
Heavy-flavour quarks are important to probe Quark-Gluon Plasma(QGP) properties. Cold Nuclear Matter(CNM) effects can be accessed by $p$Pb collisions. LHCb is a heavy-flavour precision experiment and has collected large collision data samples. Production cross-section measurements of prompt $D^{0}$ at $\sqrt{s_\mathrm{NN}}$= 5 TeV and $J/ψ$ at $\sqrt{s_\mathrm{NN}}$= 8.16 TeV are presented.
Heavy flavor production is important in heavy ion collisions to study both cold and hot nuclear matter effects. The LHCb experiment can make unique contribution to heavy ion physics, owing to the full particle identification of the detector in the forward region and the ability to collect fixed target data with proton or lead beams. This report describes recent results with proton-lead collision data collected in 2013 and the prospect of heavy-ion studies at LHCb.
In parallel to the study of proton-proton collisions, LHCb is developing a unique heavy-ion programme and is pioneering beam-gas fixed-target physics at the CERN LHC. In this document, a selection of some recent results from both programmes is presented.
The R_K measurement by LHCb suggests non-standard lepton non-universality (LNU) to occur in b -> s l+ l- transitions, with effects in muons rather than electrons. A number of other measurements of b -> s l+ l- transitions by LHCb and B-factories display disagreement with the SM predictions and, remarkably, these discrepancies are consistent in magnitude and sign with the R_K effect. Non-standard LNU suggests non-standard lepton flavor violation (LFV) as well, for example in B -> K l l' and B_s -> l l'. There are good reasons to expect that the new effects may be larger for generations closer t…
Heavy flavour physics provides excellent opportunities to indirectly search for new physics at very high energy scales and to study hadron properties for deep understanding of the strong interaction. The LHCb experiment has been playing a leading role in the study of heavy flavour physics since the start of the LHC operations about ten years ago, and made a range of high-precision measurements and unexpected discoveries, which may have far-reaching implications on the field of particle physics. This review highlights a selection of the most influential physics results on CP violation, rare dec…
The LHCb experiment is designed to study properties and decays of heavy flavored hadrons produced from $pp$ collisions at the LHC. During Run~1, it has recorded the world's largest data sample of beauty and charm hadrons, enabling precision spectroscopy studies of such particles. Several important results obtained by LHCb, such as the discovery of the first pentaquark states and the first unambiguous determination of the $Z_c(4430)^-$ as an exotic state, have dramatically increased the interest on spectroscopy of heavy hadrons. An overview of the latest LHCb results on the subject, including t…
In the last years, the \lhcb experiment established itself as an important contributor to heavy ion physics by exploiting some of its specific features. Production of particles, notably heavy flavour states, can be studied in p-p, p-Pb and Pb-Pb collisions at LHC energies in the forward rapidity region (pseudorapidity between 2 and 5), providing measurements which are highly complementary to the other LHC experiments. Moreover, owing to its forward geometry, the detector is also well suited to study fixed-target collisions, obtained by impinging the LHC beams on gas targets with different mass…
The discovery of three pentaquark peaks -- the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ -- by the LHCb collaboration has a series of interesting consequences for hadron spectroscopy. If these hidden-charm objects are indeed hadronic molecules, as suspected, they will be constrained by heavy-flavor and SU(3)-flavor symmetries. The combination of these two symmetries will imply the existence of a series of five-flavor pentaquarks with quark content $\bar{b} c s d u$ and $b \bar{c} s d u$, that is, pentaquarks that contain each of the five quark flavors that hadronize. In addition, from SU(3)-fla…
The LHCb experiment offers the unique opportunity to study heavy-ion interactions in the forward region (2 <eta< 5), in a kinematic domain complementary to the other 3 large experiments at the LHC. The detector has excellent capabilities for reconstructing quarkonia and open charm states, including baryons, down to zero $p_T$. It can separate the prompt and displaced charm components. In $p$Pb collisions, both forward and backward rapidities are covered thanks to the possibility of beam reversal. Results include measurements of the nuclear modification factor and forward-backward ratio for cha…
These proceedings summarize the LHCb measurements of charm- and beauty-hadron production in pPb collisions. The studies are made down to very low-\pt of the observed heavy-flavor hadrons using fully reconstructed decays. Nuclear matter effects are quantified via nuclear modification factors and forward-backward production ratios. A strong suppression is observed at positive rapidity (proton beam direction), while a modest or no suppression is seen for the backward rapidity (lead beam direction). The nuclear parton distributions of the lead nucleus is constrained down to Bjorken-$x\sim10^{-5}$,…
LHCb实验以7 TeV c.m.的37/pb pp碰撞开始其物理计划。LHC在2010年提供的能量。的性能和能力的实验，设想在重口味部门的精确测量，说明通过实验核心计划的第一个结果。一套丰富的生产研究提供了精确的QCD和EW测试在LHCb覆盖的独特的高快度区域。值得注意的是，W和Z生产的结果是非常令人鼓舞的部分子PDF设置约束。
We present a phenomenological analysis of asymmetric bottom- and charm-quark production within the LHCb acceptance relevant for $pp$ collisions at $\sqrt{s} = 13 \, {\rm TeV}$. Predictions are provided for both anti-$k_t$ bottom- and charm-jet pairs, which are kept differentially with respect to the invariant mass of the jet pair. It is quantified how data in this region can provide sensitivity to the couplings of the $Z$ boson to heavy quarks, and we investigate what precision is needed to compete with LEP. We also discuss how asymmetry and rate measurements can provide constraints on a parti…
The LHCb experiment has the unique possibility, among the LHC experiments, to be operated in fixed target mode, using its internal gas target SMOG. The energy scale achievable at the LHC and the excellent detector capabilities for vertexing, tracking and particle identification allow a wealth of measurements of great interest for cosmic ray and heavy ions physics. We report the first measurements made in this configuration: the measurement of antiproton production in proton-helium collisions and the measurements of open and hidden charm production in proton-argon collisions at $\sqrt{s_\textrm…
I report new, world-leading LHCb results on heavy meson lifetimes. We use a novel approach that suppresses the shortcomings typically associated with reconstruction of semileptonic decays, allowing for precise measurements of lifetimes and other properties in collider experiments. We achieve a 15% and a $2\times$ improvement over current best determinations of the flavor-specific $B^0_s$ lifetime and $D^-_s$ lifetime, respectively.
We consider the ${\bar D}^{(*)}Σ_c^{(*)}$ states, together with $J/ψN$ and other coupled channels, and take an interaction consistent with heavy quark spin symmetry, with the dynamical input obtained from an extension of the local hidden gauge approach. By fitting only one parameter to the recent three pentaquark states reported by the LHCb collaboration, we can reproduce the three of them in base to the mass and the width, providing for them the quantum numbers and approximate molecular structure as $1/2^-$ $\bar{D} Σ_c$, $1/2^-$ $\bar{D}^* Σ_c$, and $3/2^-$ $\bar{D}^* Σ_c$, and isospin $I=1/…
We report recent results by the LHCb collaboration in heavy-ion collisions in collider and fixed-target mode at the LHC. A large variety of measurements show the potential of LHCb in nuclear collisions.
We assess the impact of searches at flavor factories for new neutral resonances that couple to both photons and gluons. These are well motivated by "heavy axion" solutions of the strong CP problem and by frameworks addressing both Dark Matter and the Higgs hierarchy problem. We use LHCb public diphoton data around the Bs mass to derive the current best limit on these resonances for masses between 4.9 and 6.3 GeV. We estimate that a future LHCb dedicated search would test an axion decay constant of O(TeV) for axion masses in the few-to-tens of GeV, being fully complementary to the low mass ATLA…
The LHCb experiment measured the time-dependent CP asymmetries $C_{KK}$ and $S_{KK}$ in $B_s\to K^+K^-$ decay. Combining with the corresponding CP asymmetries $C_{ππ}$ and $S_{ππ}$ in $B\to π^+π^-$ decay, we find that the size of $U$-spin breaking in this system is of order $20\%$. Moreover, the data suggest that these effects are dominated by factorizable contributions. We further study the constraints on new physics contributions to $b\to u\bar uq$ ($q=s,d$). New physics that is minimally flavor violating (MFV) cannot be distinguished from the Standard Model (SM) in these decays. However, ne…
High-precision electroweak production measurements from the Tevatron and the LHC provide important constraints on the quark flavor separation in global PDF fits. In this contribution, we study the impact of the recent D0 W asymmetry measurements and of the LHCb W and Z Run I combination in the global NNPDF analysis. We find that these measurements can be described by NLO QCD theory and that they lead to a significant reduction of PDF uncertainties.
This article presents recent results of the Z boson production in the proton-lead collisions and the charmonium production in the ultra-peripheral lead-lead collisions at the LHC collected during 2013 to 2018 by the LHCb detector. The potential heavy ion programs in these topics are also discussed.
We calculate differential cross sections for $c \bar c$- and $b \bar b$-dijet production in $pp$-scattering at $\sqrt{s} = 13$ TeV in the $k_T$-factorization and hybrid approaches with different unintegrated parton distribution functions (uPDFs). We present distributions in transverse momentum and pseudorapidity of the leading jet, rapidity difference between the jets and the dijet invariant mass. Our results are compared to recent LHCb data on forward production of heavy flavour dijets, measured recently for the first time individually for both, charm and bottom flavours. We found that an agr…
This paper reports a study of the experimental signatures of hierarchical sectors beyond the Standard Model characterized by a flavor-violating heavy vector and a set of light pseudo-Goldstone bosons $a_{1,2}$, spanning a large range of lifetimes. The non-minimal scalar spectrum triggers novel $B$ decays into multiple leptons that would have escaped the reach of current searches. Novel displaced vertex analyses at LHCb are therefore discussed to probe the hierarchical new physics, extending the scope of the tracking system of the detector. Additionally, the reach of the proposed CODEX-b experi…
Beauty tetraquark states $X(\bar b q'q'' \bar q )$ composed of $ \bar b s u \bar d$, $\bar b d s \bar u$, and $\bar b u d \bar s$, are unique that all the four valence quarks are different. Although the claim of existence of the first two states by D0 was not confirmed by data from LHCb, the possibility of such states still generated a lot of interests and should be pursued further. Non-observation of $X(\bar b q'q'' \bar q )$ states by LHCb may be just due to a still lower production rate than the limit of LHCb or at some different mass ranges. In this work we use light quark $SU(3)$ flavor s…
The spectrum of the doubly heavy baryons is estimated with respect to the new observation from the LHCb collaboration [Aaij:2017ueg] by using the chiral partner structure and heavy quark spin-flavor symmetry. The effects of heavy quark flavor symmetry breaking and light quark flavor symmetry are considered. The mass splitting of doubly heavy baryons with the same spin but opposite parity arises from the generalized Goldberger-Treiman relation. The intermultiplet one-pion transition and intramultiplet radiative transitions are also be estimated.
