S. Frixione
I discuss the current status of the comparison between theoretical predictions and experimental data, relevant to the production of open charm and bottom quarks in photon-hadron and photon-photon collisions. I advocate the use of a formalism that matches fixed-order computations to resummed computations in order to make firm statements on heavy flavour production as described by perturbative QCD.
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We comment on the power of the 'standard' solutions to the SUSY flavour and CP problem based on supergravity and its derivates like mSUGRA in comparison to the flavour symmetry approach. It is argued that flavour symmetries, and SU(3) in particular, can not only mimic the situation in supergravity frameworks in this respect, but sometimes do even better providing at the same time a further link between the soft and Yukawa sectors, that could be testable at future experimental facilities.
A composite Higgs boson of 125 GeV mass, only mildly fine-tuned, requires top partners with a semi-perturbative coupling and a mass not greater than about a TeV. We analyze the strong constraints on such picture arising from flavour and electroweak precision tests in models of partial compositeness. We consider different representations for the composite fermions and compare the case of an anarchic flavour structure to models with a U(3)^3 and U(2)^3 flavour symmetry. Although non trivially, some models emerge that look capable of accommodating a 125 GeV Higgs boson with top partners in an int…
I summarize the theory talks given in the Heavy Flavours Working Group. In particular, I discuss heavy-flavour parton distribution functions, threshold resummation for heavy-quark production, progress in fragmentation functions, quarkonium production, heavy-meson hadroproduction.
We present a short review of heavy flavours and the main challenges given the recent experimental developments.
I review recent developements in the theory of heavy flavour production. In particular, I dicuss the next-to-leading resummation of soft gluon effects in heavy flavour hadroproduction, and the next-to-leading resummation of collinear radiation in the production of heavy flavour at large transverse momenta.
Recent issues in heavy flavour physics are reviewed. Anomalies in charmonium, $B$, and $Υ(5S)$ decays and production are highlighted. New results concerning exotic heavy quark states are also briefly reviewed.
The molecular picture and the constituent-quark model of exotic hadrons are reviewed, with application to the states recently discovered in the hidden-charm and hidden beauty sectors, and to other configurations.
I discuss few recent developments in Heavy Flavour Production phenomenology.
We present an approximate NNLO evaluation of the QCD form factor resumming large logarithmic perturbative contributions in semi-inclusive heavy flavour decays.
Heavy flavours production in e-p DIS is studied at intermediate values of the transferred four-momentum square, under the assumption of boson-gluon-fusion mechanism dominance (no intrinsic heavy flavours contributions). In this framework different expressions for the splitting functions in the gluon density evolution equation, with respect to the standard (DGLAP) ones, are explicitly derived.
This is a summary of the contributions presented in the Heavy Flavours Working Group of the DIS2006 Workshop.
Recent progress in the theoretical description of inclusive heavy flavour decays is reviewed. After an outline of the theoretical methods applications to total decay rates and semileptonic decay spectra are presented.
We review some rigourous consequences of flavour independence on the spectrum and properties of hadrons in potential models, with emphasis on hadrons with two heavy quarks, such as $(b\bar c)$ mesons and $(QQq)$ baryons.
We discuss three theoretical schemes to describe charm quark electroproduction.
We review the status of heavy flavour production in QCD. Comparison of experimental and theoretical results for top and bottom production are given. Selected topics in charm production are also discussed.
This is the first part of lectures about effective field theories. Decoupling of heavy-particle loops is considered (heavy leptons in QED, heavy quarks in QCD).
We show that the quark flavour structure and CP violating phenomena are strongly correlated in supersymmetric theories. For a generic pattern of supersymmetry breaking the two broad categories of Yukawa couplings, democratic and hierarchical textures, have entirely different phenomenological implications. With hierarchical Yukawas, the rephasing invariant phase, arg(V_us V_cb V_cb^* V_cs^*), in the CKM mixing matrix has to be of order unity, while the SUSY CP violating phases are severely constrained by electric dipole moments, giving rise to the so-called SUSY CP problem. With democratic Yuka…
We discuss the impact of the planned upgrades of the HERA collider on the study of open heavy flavour and quarkonium production. New experimental techniques in charm physics are presented.
Measurements in heavy-flavour azimuthal angular correlation provide insight into the production, propagation, and hadronization of heavy-flavour jets in ultra-relativistic hadronic and heavy-ion collisions. These measurements across different particle species help to isolate the possible modification in particle production and fragmentation due to different mass and quark contents. Jet correlation studies give direct access to the initial parton dynamics produced in these collisions. \\ This article studies the azimuthal angular correlations of heavy-flavour hadrons (charm and beauty mesons an…
O(α) QED radiative corrections to polarized neutral current leptoproduction of heavy quark flavours are calculated in the leading log approximation for HERMES, COMPASS, and HERA kinematics. Besides the inclusive case, we derive general $z_h$-differential formulae for the polarized boson gluon fusion process and use them to calculate radiative corrections to semi-inclusive polarized heavy flavour production in the case of HERA kinematics.
Starting from fixed-order perturbation theory (FOPT) we derive expressions for the heavy-flavour components of the deep-inelastic structure functions FL and F2 in the variable-flavour number scheme (VFNS). These expressions are valid in all orders of perturbation theory. This derivation establishes a relation between the parton densities parametrized at N and N light flavours. The consequences for the existing parametrizations of the parton densities are discussed. Further we show that in charm electroproduction the exact and asymptotic expressions for the heavy-quark coefficient functions yie…
In this thesis we describe the calculation of the process e+ e- --> Z/gamma -> Q Qbar + X, where Q is a heavy quark, X is anything else at order alpha_s^2.
It is shown that the $μ^{\pm}$ originating from the decay of heavy-flavour mesons in the simulated proton-proton collisions at $\sqrt{s} = 13$ TeV using the PYTHIA 8 event generator can be made into two groups based on the value of their light front variable such that one among these two groups of $μ^{\pm}$ follow the Boltzmann statistics with a nearly isotropic angular distribution. A similar effect is not observed for $e^{\pm}$ from the decay of heavy-flavour mesons in these collisions.
Studies presented in the heavy flavours working group are summarized. Very recent results of measurements at the HERA, LHC, Tevatron, STAR, PHENIX, and BaBar experiments are reviewed and new developments in theory and phenomenology are discussed. In particular, aspects of the impact of heavy flavours on global QCD analyses to determine the structure of the proton, and analyses in physics beyond the Standard Model are considered.
The current status of the theory and phenomenology of weak decays of hadrons containing a heavy quark is reviewed. Exclusive semileptonic and rare decays of $B$ mesons are discussed, as well as inclusive decay rates, the semileptonic branching ratio of the $B$ meson, and the lifetimes of $b$-flavoured hadrons. Determinations of $α_s$ from $Υ$ spectroscopy are briefly presented.
AT HERA heavy quarks may contribute up to 30% of the structure function $F_2$. The introduction of heavy quarks requires an extension of the DGLAP formalism. The effect of using different heavy flavour number schemes, and different approaches to the running of $α_s$, are compared using the ZEUS PDF fit formalism. The potential of including charm data in the fit is explored, using $D^*$ double differential cross-sections rather than the inclusive quantity $F_2^{c\bar{c}}$.
I review some topics in the production and decays of heavy flavours that are relevant for collider physics. In particular, I discuss the present status and some recent progress related to masses, parton densities and fragmentation functions of heavy quarks, as well as threshold resummation, polarized onium production at high transverse momentum, and a factorization theorem for $B \toππ$ decays.
The absorptive corrections resulting from the rescattering of a heavy flavour (the so-called nuclear absorption) are usually calculated with a probabilistic formula valid only in the low energy limit. We extend this formula to all energies using a quantum field theoretical approach. For charmonium and bottonium we find that the absorptive corrections in the rigorous treatment are very similar to the ones in the probabilistic approach. On the contrary, at sufficiently high energy, open charm and bottom are absorbed as much as charmonium and bottonium - in spite of the fact that their absorptive…
Recent progress in Heavy Flavour Production phenomenology are discussed. In particular, the long-standing discrepancy of the Tevatron b production data is considered. It is shown that a better use of e^+e^- data in constraining the effect of fragmentation reduces the discrepancy considerably.
In analogy with parton distribution functions, also parton fragmentation functions obey matching conditions when crossing heavy-flavour thresholds. We compute these matching conditions at next-to-leading order in the strong coupling constant alpha_s in the MSbar scheme. Our results can be used for the dynamical generation of the heavy-flavour component in next-to-leading order fits to light-hadrons fragmentation functions. Furthermore, when computing perturbatively the charm fragmentation function from first principles and evolving it to higher scales, our matching conditions should be used fo…
We present results for the quenching, elliptic flow and azimuthal correlations of heavy flavour particles in high-energy nucleus-nucleus collisions obtained through the POWLANG transport setup, developed in the past to study the propagation of heavy quarks in the Quark-Gluon Plasma and here extended to include a modeling of their hadronization in the presence of a medium. Hadronization is described as occurring via the fragmentation of strings with endpoints given by the heavy (anti-)quark Q(Qbar) and a thermal parton qbar(q) from the medium. The flow of the light quarks is shown to affect sig…
We report the masses of $B$ and $D$ sectors heavy-flavoured mesons obtained by using our recently developed meson wave function employing potential model approach with linear confinement term in potential as parent in the perturbation method. As the wave-function involves infinite Airy's polynomial series, in carrying out the mass calculation, to avoid divergences, we have introduced some cut-off parameter for inter-quark separation. Our results for ground state masses of heavy-flavoured $B$ and $D$ sector mesons are reasonably closer to the PDG masses.
Uses of QCD sum rules for heavy flavoured hadrons are discussed. "Standard" applications such as the determination of the $b$, $c$ quark masses, the calculation of $f_B$, $f_D$ and of the heavy-to-light form factors are overviewed. Furthermore, a new approach to calculate the $B\to ππ$ hadronic matrix elements from QCD light-cone sum rules is described.
We reconsider the role that the possible detection of lepton flavour violating (LFV) decays of supersymmetric particles at the Large Hadron Collider (LHC) can play in helping reconstruct the underlying neutrino mass generation mechanism within the simplest high-scale minimal supergravity (mSUGRA) seesaw schemes. We study in detail the LFV scalar tau decays at the LHC, assuming that the observed neutrino masses arise either through the pure type-I or the simpler type-II seesaw mechanism. We perform a scan over the mSUGRA parameter space in order to identify regions where lepton flavour violatin…
In this paper we describe the calculation of the process e+e- -> Z/gamma -> QQbar + X, where Q is a heavy quark, at order alpha_s^2.
The Thorne-Roberts variable flavour number scheme (VFNS) for heavy quarks is presented in detail for the specific case of charged current DIS. As in neutral current DIS this provides a smooth extrapolation from the fixed flavour number scheme (FFNS) appropriate at low $Q^2$ to the zero-mass variable flavour number scheme (ZM-VFNS) appropriate as $Q^2 \to \infty$, and differs from alternative versions of a VFNS by the definition of the coefficient functions at each order, and the strict ordering of the expansion in $α_S$. However, there are subtle differences from the neutral current case which…
In minimal supergravity (mSugra), the neutrino sector is related to the slepton sector by means of the renormalization group equations. This opens a door to indirectly test the neutrino sector via measurements at the LHC. Concretely, for the simplest seesaw type-I, we present the correlations between seesaw parameters and ratio of stau lepton flavour violating (LFV) branching ratios. We find some simple, extreme scenarios for the unknown right-handed parameters, where ratios of LFV rates correlate with neutrino oscillation parameters. On the other hand, we scan the mSugra parameter space, for …
Triply heavy flavour baryons are studied using the hyper central description of the three-body system. The confinement potential is assumed as hyper central coulomb plus power potential with power index $p$. The ground state ($J^P={1/2}^+$ and ${3/2}^+$) masses of heavy flavour baryons are computed for different power index, $ p$ starting from 0.5 to 2.0. The predicted masses are found to attain a saturated value with respect to variation in $p$ beyond the power index $p>1.0$. Using the spin-flavour structure of the constituting quarks and by defining effective mass of the confined quarks with…
We consider the transverse-momentum distribution of heavy flavours in photon-hadron collisions. We present a formalism in which large transverse-momentum logarithms are resummed to the next-to-leading level, and mass effects are included exactly up to order alpha_em alpha_s^2, so as to retain predictivity at both small and large transverse momenta. Phenomenological applications relevant to charm photoproduction at HERA are given.
We consider the transverse-momentum distribution of heavy flavours in hadronic collisions. We present a formalism in which large transverse-momentum logarithms are resummed at the next-to-leading level, and mass effects are included exactly up to order α_strong^3, so as to retain predictivity at both small and large transverse momenta. As an example, we apply our formalism to b production at the Tevatron.
We review the Spring 2022 status of the current $B$ anomalies and their possible interpretation in terms of New Phsyics. We also discuss the discovery potential of targeted LHC and future collider searches for the underlying new particles and their complementarity with low-energy flavour observables.
Within the framework of nonrelativistic quark-antiquark Cornell potential model formalism, we study the annihilation of heavy quarkonia. We determine their annihilation widths resulting into digluon, dilepton, $3γ$, $3g$ and $γgg$ and compare our findings with the available theoretical results and experimental data. We also provide the charge radii and absolute square of radial Schrödinger wave function at zero quark-antiquark separation for heavy quarkonia and $B_c$ mesons.
In a series of three lectures, I review the theory and phenomenology of heavy quark masses and mixing angles and the status of their determination. In addition, I give an introduction to heavy quark symmetry, with the main emphasis on the development of heavy quark effective field theory and its application to obtain a model-independent determination of $|V_{cb}|$.
We present a next-to-leading order calculation of heavy flavour production in hadronic collisions that can be interfaced to shower Monte Carlo programs. The calculation is performed in the context of the POWHEG method. It is suitable for the computation of charm, bottom and top hadroproduction. In the case of top production, spin correlations in the decay products are taken into account.
In the asymptotic limit $Q^2 \gg m^2$, the non-power corrections to the heavy flavour Wilson coefficients in deep--inelastic scattering are given in terms of massless Wilson coeffcients and massive operator matrix elements. We start extending the existing NLO calculation for these operator matrix elements by calculating the O($ε$) terms of the two--loop expressions and having first investigations into the three--loop diagrams needed to O($α_s^3$).
The recent theory developments and latest experimental results on heavy-flavour production in Deep Inelastic Scattering and at hadron colliders are summarized. Models of heavy quarkonia production, non-perturbative corrections to fragmentation, theory of heavy-hadron production in heavy-ion collisions, and interpretation of new exotic hadrons are discussed. Progress in event generators development is reported. Most recent experimental results from HERA and e+e- colliders as well as from proton-(anti)proton and heavy ion experiments are presented and the role of charm and beauty quarks in the a…
Motivated by the recent developments in stability of hydrogen atom in a space with one finite extra-dimension,we consider that physical mesons are also stable in such a space and estimate their masses in a QCD inspired potential model. Our analysis suggests that a model of mesons with linear plus coulomb potential in a space with one finite extra-dimension of size very very less than 10^{-18} m is compatible with the present experimental data of heavy flavour mesons.
A theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology as it applies to total lifetimes and the underlying theoretical issues are sketched. Predictions are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than expected. The ramifications of those findings are analyzed in detail.
At the HERA collider at DESY, high energy electron and positron beams interact with proton beams. A review is presented of the variety of ways in which these collisions produce final states containing charm and beauty quarks.
We have calculated the first and second order corrections to several deep inelastic sum rules which are due to heavy flavour contributions. A comparison is made with the existing perturbation series which has been computed up to third order for massless quarks only. In general it turns out that the effects of heavy quarks are very small except when $Q \sim m$ or $Q \gg m$. Here $Q$ and $m$ denote the virtual mass of the vector boson and the mass of the heavy quark, respectively. For $Q \gg m$ the radiative corrections reveal large logarithms of the type $\ln Q^2/m^2$ which have to be absorbed …
Two AdS/CFT based energy loss models are used to compute the suppression and azimuthal correlations of heavy quarks in heavy ion collisions. The model with a velocity independent diffusion coefficient is in good agreement with B and D meson data up to high $p_T$. The partonic azimuthal correlations we calculate exhibit an order of magnitude difference in low momentum correlations to pQCD calculations [arXiv:1305.3823]. We thus propose heavy flavour momentum correlations as a distinguishing observable of weakly- and strongly-coupled energy loss mechanisms.
Due to the large masses of the charm and bottom quarks, their production cross sections are calculable within the perturbative QCD. This makes the heavy-quark mesons important observables in high-energy collisions of protons and nuclei. However, the available calculations for heavy-flavored-meson hadroproduction have been somewhat problematic in reliably describing the cross sections across the full kinematic range from zero to very high $p_{\rm T}$. This has put some question marks on the robustness of LHC heavy-flavored-meson measurements in studying the partonic structure of the colliding h…
We present analytical results for master integrals emerging in the computation of differential rates for inclusive weak decays of heavy flavors at next-to-leading order (NLO) in QCD. As an immediate physical application, these master integrals allow for a calculation of the spectra of the leptonic invariant mass in inclusive semileptonic decays in the framework of the heavy quark expansion, including the NLO QCD corrections to power suppressed terms.
The DGLAP improved saturation model of Bartels, Golec and Kowalski is supplemented by the contribution from the heavy quarks: charm and beauty. It is shown to give good description of both the total proton structure function F2 and, as a prediction, the heavy quarks contribution F2c and F2b. The reasonable agreement for the longitudinal and diffractive structure functions is also found.
We consider the phenomenology at the Large Hadron Collider of new heavy vector-like quarks which couple mainly to the third generation quarks via Yukawa interactions, with special emphasis on non-standard doublet representations which are less constrained from present data. We also discuss in detail the flavour limits at tree level and loop level and implications of a generalised CKM mixing matrix to these cases.
The LHC data on the forward heavy flavour hadron production can be a new unique source for estimation of intrinsic charm and bottom contributions to the proton. For example, we analyze the forward heavy baryon production, namely $Λ_b$-baryon, within the soft QCD quark gluon string model and present the predictions for observables which could be measured at the LHC. We also present some predictions for the $D$-meson production in $pp$ collisions made within the perturbative QCD including the intrinsic charm in the proton that can be verified at the LHC.
We review the production of charm and bottom quarks in two-photon collisions at e+e- colliders. The next-to-leading order QCD predictions for total cross sections and differential distributions are compared with recent experimental results.
Recent results from H1 and ZEUS on heavy flavour production at HERA are reviewed
A personal account of possible implications of recent heavy flavour measurements is given.
A summary of the latest experimental results in heavy flavour physics is presented.
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