We calculate single parton distributions inside quark and gluon jets within the coherent branching formalism, which resums leading and next-to-leading logarithmic contributions. This formalism is at the basis of the modified leading logarithmic approximation (MLLA), and it conserves energy exactly. For a wide preasymptotic range of the evolution variable Y=ln[Eθ/Q_0], we find marked differences in the shape and norm of single parton distributions calculated in the MLLA or in the coherent branching formalism, respectively. For asymptotically large values Y>5-10, the difference in norm persists, while differences in shape disappear. In this way, our numerical study delineates the jet energy scale needed for a reliable application of both approaches. We also study the dependence of the single parton distributions on the hadronization scale Q_0 and on Λ_QCD, and we calculate within the coherent branching formalism the identified quark and gluon distributions inside quark and gluon jets.
Calculations of Drell-Yan (DY) production at next-to-leading (NLO) order have been combined with Transverse Momentum Dependent (TMD) distributions obtained with the Parton Branching (PB). The predictions show a remarkable agreement with DY measurement from E605 experiment, consistent with previous results we obtained for R209, PHENIX, CMS and ATLAS experiments. We also present predictions for Z+jet measurements showing the importance of TMD parton shower contributions to the jet multiplicity. We show that PB-TMD parton density and the corresponding PB-TMD parton shower can be combined with lea…
ECOMB is established as a hadronic multiparticle production generator by soft interaction. It incorporates the eikonal formalism, parton model, color mutation, branching, resonance production and decay. A partonic cluster, being color-neutral initially, splits into smaller color-neutral clusters successively due to the color mutation of the quarks. The process stops at hadronic resonance, $q\bar q$ pair, formation. The model contains self-similar dynamics and exhibits scaling behavior in the factorial moments, e.g. the intermittency.
QCD predictions for final states with multiple jets in hadron collisions make use of multi-jet merging methods, which allow one to combine consistently the contributions from hard scattering matrix elements with different parton multiplicities and parton showers. In this article I consider a multi-jet merging method that has recently been proposed to take into account the effects of transverse momentum dependent (TMD) evolution and parton shower, and present studies focusing on the application of this method to jets associated with Drell-Yan (DY) production in the region of high masses.
We present the first calculation of the momentum sharing and angular separation distributions between the leading subjets inside a reconstructed jet in heavy ion collisions. These observables are directly sensitive to the hardest branching in the process of jet formation and are, therefore, ideal for studying the early stage of the in-medium parton shower evolution. The modification of the momentum sharing and angular separation distributions in lead-lead relative to proton-proton collisions is evaluated using the leading-order medium-induced splitting functions obtained in the framework of so…
The azimuthal correlation, $Δϕ_{12}$, of high transverse momentum jets in pp collisions at $\sqrt{s}=13$ TeV is studied by applying PB-TMD distributions to NLO calculations via MCatNLO together with the PB-TMD parton shower. A very good description of the cross section as a function of $Δϕ_{12}$ is observed. In the back-to-back region of $Δϕ_{12} \to π$, a very good agreement is observed with the PB-TMD Set 2 distributions while significant deviations are obtained with the PB-TMD Set 1 distributions. Set 1 uses the evolution scale while Set 2 uses transverse momentum as an argument in $α_s$, a…
The Parton Branching (PB) Method describes the evolution of transverse momentum dependent parton densities (TMDs). The obtained TMDs can be used in Monte Carlo generators to describe physical observables. We give an overview of recent developments, in particular the new application of PB TMDs in Drell-Yan + jets production, the four-flavor and five-flavor schemes for heavy quark contributions, and the inclusion of QED corrections in the PB evolution.
An interpretation of scale-invariant multiplicity fluctuations inside hadronic jets is presented. It is based on the branching mechanism with the angular ordering of soft partons in sequential branchings. A relationship with fractal distributions is demonstrated. The model takes into account the finiteness of the number of particles produced in jets (finite energy) and leads to a good description of the multifractal fluctuations observed in E+E- processes.
The parton branching formulation of TMD evolution has recently been used to make predictions for jet observables at the Large Hadron Collider (LHC), including perturbative matching at next-to-leading order (NLO). This contribution presents results for the azimuthal Δ-ϕcorrelations in events with di-jets at large transverse momentum. It focuses on the back-to-back region of large Δ-ϕand discusses prospects for detailed studies of QCD dynamics in this region at the LHC.
Profiling the Higgs boson requires the study of its non-standard decay modes. In this work we discuss the prospects of the Large Hadron electron Collider (LHeC) to detect scalar particles with masses $\gtrsim$ 10 GeV produced from decays of the Standard Model (SM) Higgs boson. These scalar particles decay mainly to bottom pairs, and in a vast portion of the allowed parameter space they acquire a macroscopic lifetime, hence giving rise to displaced hadronic vertices. The LHeC provides a very clean environment that allows for easy identification of these final states, in contrast to hadronic col…
We study infrared (IR) divergences in light front quantum chromodynamics using a coherent state basis in light front time-ordered Hamiltonian perturbation theory. In computation of the S-matrix elements in Hamiltonian formalism, the IR divergences appear in the form of vanishing energy denominators. We consider the process $e^{+}e^{-}\rightarrow 2\; jets$ at $\mathcal{O}(g^{2})$ in strong coupling, construct the coherent state representing the outgoing particles, and explicitly show that the `true' IR divergences cancel to this order when the matrix elements are calculated between coherent sta…
Progress in the theoretical understanding of parton branching dynamics within an expanding Quark Gluon Plasma relies on detailed and fair comparisons with experimental data for reconstructed jets. Such comparisons are only meaningful when the computed jet, be it analytically or via event generation, accounts for the complexity of jets reconstructed in the challenging environment of heavy-ion collisions. Jet reconstruction in heavy ion collisions involves a necessarily imperfect subtraction of the large and fluctuating underlying event: reconstructed jets always include underlying event contami…
We studied the evolution of jets within a medium that contains both, transverse kicks as well as medium induced coherent radiation. In this framework parton branching occurs simultaneously to scatterings within the medium, leading to the interference effects that reproduce the well known BDMPS-Z emission rates and sizeable transverse momentum broadening. We examined the relative importances of transverse momentum broadening from the coherent splittings and different types of in-medium scatterings and found a clear hierarchy of the influences from different scattering effects and deflections du…
The decays of pseudoscalar bottomonium eta_b into a pair of vector charmonia, J/ψJ/ψ, J/ψψ', ψ' ψ' are considered in the light cone formalism. Relativistic and leading logarithmic radiative corrections to the amplitudes of these processes are resummed. It is shown that the small value for the branching ratio of the decay eta_b-> J/ψJ/ψobtained within the leading order nonrelativistic QCD is a consequence of a fine-tuning between certain parameters, which is broken when relativistic and leading logarithmic radiative corrections are taken into account. As a result, the branching ratio obtained i…
I report on precision comparisons of theoretical predictions for Drell-Yan (DY) transverse momentum spectra from two approaches: the analytical resummation approach based on Collins-Soper-Sterman (CSS) formalism and the parton branching (PB) approach to the evolution of transverse momentum dependent (TMD) parton distributions.
One of the main theoretical systematics in studies of final states with large jet multiplicities at high-energy hadron colliders is associated with the merging of QCD parton showers and hard-scattering matrix elements. We present a method to incorporate the physics of transverse momentum recoils due to initial-state shower evolution into multi-jet merging algorithms by using the concept of transverse momentum dependent (TMD) distributions and the associated parton branching. We investigate the dependence on the merging scale and illustrate the impact of the new method at the level of both excl…
We investigate parton-branching methods based on transverse-momentum dependent (TMD) parton distributions and matrix elements for the Monte Carlo simulation of multi-particle final states at high-energy colliders. We observe that recently measured angular correlations in ep final states with multiple hadronic jets probe QCD coherence effects in the space-like branching, associated with finite-angle gluon radiation from partons carrying small longitudinal momenta, and not included in standard shower generators. We present Monte Carlo calculations for azimuthal two-jet and three-jet distribution…
We give a pedagogical review of recent progress towards understanding the response of a strongly coupled plasma at finite temperature to a hard probe. The plasma is that of the N=4 supersymmetric Yang-Mills theory and the hard probe is a virtual photon, or, more precisely, an R-current. Via the gauge/gravity duality, the problem of the current interacting with the plasma is mapped onto the gravitational interaction between a Maxwell field and a black hole embedded in the AdS_5 x S^5 geometry. The physical interpretation of the AdS/CFT results can be then reconstructed with the help of the ultr…
Given its weak coupling to bottom quarks and tau leptons, the Higgs boson may predominantly decay into invisible particles like gravitinos, neutralinos, or gravitons. We consider the manifestation of such an invisibly decaying Higgs boson in weak boson fusion at the CERN LHC. Distinctive kinematic distributions of the two quark jets of the signal as compared to Zjj and Wjj backgrounds allow to restrict the Higgs branching ratio to 'invisible' final states to some 13% with 10fb^{-1} of data, provided events with two energetic forward jets of high dijet invariant mass and with substantial missin…
We study radiative decays of $Υ$ to light quark jets in nonrelativistic QCD by taking both the color singlet and color octet $b\bar b$ operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about $36^\circ$, the branching ratio for $Υ\toγq\bar q$ is found to be $8.2\times 10^{-4}$ from color singlet contributions. The color octet contributions could be mu…
We present a study of the Higgs boson decay branching ratios to $b\bar{b}$, $c\bar{c}$ and gluons, one of the cornerstones of the physics program at the International Linear Collider (ILC). A standard model Higgs boson of 120\,GeV mass, produced in the Higgs-strahlung process at $\sqrt{s} = 250$\,GeV was investigated using the full detector simulation and reconstruction procedures. The analysis was performed in the framework of the Silicon Detector (SiD) concept with full account of inclusive standard model backgrounds. The selected decay modes contained two heavy flavour jets in the final sta…
We present the calculation of the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's shock-wave formalism. We also rederive the impact factor for photon to quark and antiquark transition. These results provide the necessary building blocks for further phenomenological studies of inclusive diffractive deep inelastic scattering as well as for two and three jets diffractive production which go beyond approximations discussed in the literature.
We present a new formalism for parton shower simulation of QCD jets, which incorporates the following features: invariance under boosts along jet axes, improved treatment of heavy quark fragmentation, angular-ordered evolution with soft gluon coherence, more accurate soft gluon angular distributions, and better coverage of phase space. It is implemented in the new HERWIG++ event generator.
We discuss coherent QCD radiation from space-like parton branching and its effects on multi-jet final states at high-energy hadron colliders. Coherence effects for small longitudinal momentum fractions x are not included in the branching algorithms of standard shower Monte Carlo event generators. On the other hand, they are taken into account only partially in perturbative next-to-leading-order calculations for multi-jets. Such effects are present to all orders in alpha_s and can become logarithmically enhanced with \sqrt{s} / E_T, where E_T is the hardest jet transverse energy. We present res…
We study the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's shock-wave formalism. Our aim is to extend existing results beyond approximations discussed in the literature. We present our results of the real contribution, and present some intermediate results on virtual contributions for the photon to quark, antiquark transition.
We present an algorithm that evolves hard processes at the amplitude level by dressing them iteratively with (massless) quarks and gluons. The algorithm interleaves collinear emissions with soft emissions and includes Coulomb/Glauber exchanges. It includes all orders in $N_{\mathrm{c}}$, is spin dependent and is able to accommodate kinematic recoils. Although it is specified at leading logarithmic accuracy, the framework should be sufficient to go beyond. Coulomb exchanges make the factorisation of collinear and soft emissions highly non-trivial. In the absence of Coulomb exchanges, we show ho…
We investigate the decay properties of some beauty and charm mesons with a phenomenological potential model. First, we consider the nonrelativistic Hamiltonian of the mesonic system with Coulomb plus exponential terms and study the wave function and the energy of the system using the variational approach. Thereby, we compute the masses, the decay constants, the leptonic branching fractions of heavy-light mesons and the mixing mass parameter $Δ{m_{B_q}}$. We study the radiative leptonic decay widths of ${D_s} \to γ\ell \bar ν$, ${D^ - } \to γ\ell \bar ν$ and the semileptonic decay widths of ${\…
The remarkable agreement of electroweak data with standard model (SM) predictions motivates the study of extensions of the SM in which the Higgs boson is light and couples in a standard way to the weak gauge bosons. Postulated new light particles should have small couplings to the gauge bosons. Within this context it is natural to assume that the branching fractions of the light SM-like Higgs boson mimic those in the standard model. This assumption may be unwarranted, however, if there are non-standard light particles coupled weakly to the gauge bosons but strongly to the Higgs field. In parti…
The suppression of single jets at high transverse momenta in a quark-gluon plasma is studied at RHIC energies, and the additional information provided by a photon tag is included. The energy loss of hard jets traversing through the medium is evaluated in the AMY formalism, by consistently taking into account the contributions from radiative events and from elastic collisions at leading order in the coupling. The strongly-interacting medium in these collisions is modelled with (3+1)-dimensional ideal relativistic hydrodynamics. Putting these ingredients together with a complete set of photon-pr…
In view of future phenomenological applications, we study the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's shock-wave formalism. The aim of the present program is to extend existing results beyond approximations discussed in the literature. We present our results of the real contribution, and report on recent progress in calculating the virtual contributions for the photon to quark, antiquark transition.
We study the cross section for dijet production via direct photons, as seen at the HERA collider. Rather than assuming the standard factorisation formula for the cross section (where the incoming partons are assumed to be on-shell), we use the $k_T$-factorisation formula. This formalism ought to be more appropriate for jet production in regions where the cross section is sensitive to the small-$x$ parton distribution functions. We study the rapidity distribution and the azimuthal angular distribution of the jets and compare with the traditional approach. Our calculations reveal a breakdown of …
To offer a possible resolution to the apparent discrepancy between the experimental and the theoretical values of the $W + 1$ jet to $W + 0$ jets ratio reported by the \D0 group, we examine the effects of the multiple soft gluon radiation on the $W$ boson production at the Tevatron. Based on the calculation of the $W$ boson transverse momentum ($Q_T$) distribution in the Collins-Soper-Sterman resummation formalism, we conclude that the effect of the soft gluon radiation is important in the region of $Q_T < 50$ GeV, and it can be better tested by a more inclusive observable $R_{CSS}(Q_T^{\min})…
Calculations using the AdS/CFT correspondence can be used to unveil the short-distance structure of a strongly coupled plasma, as it would be seen by a `hard probe'. The results of these calculations admit a natural physical interpretation in terms of parton evolution in the plasma: via successive branchings, essentially all partons cascade down to very small values of the longitudinal momentum fraction x and to transverse momenta smaller than the saturation momentum Q_s\sim T/x. This scale Q_s controls the energy loss and the transverse momentum broadening of an energetic jet propagating thro…
We calculate the leading corrections to jet momentum broadening and medium-induced branching that arise from the velocity of the moving medium at first order in opacity. These results advance our knowledge of jet quenching and demonstrate how it couples to collective flow of the quark-gluon plasma in heavy-ion collisions and to the orbital motion of partons in cold nuclear matter in deep inelastic scattering at the electron-ion collider. We also compute the leading corrections to jet momentum broadening due to transverse gradients of temperature and density. We find that these effects lead to …
In this paper, we present a more detailed version of our previous work for three-particle correlations in quark and gluon jets [1]. We give theoretical results for this observable in the double logarithmic approximation and the modified leading logarithmic approximation. In both resummation schemes, we use the formalism of the generating functional and solve the evolution equations analytically from the steepest descent evaluation of the one-particle distribution. In addition, in this paper we include predictions beyond the limiting spectrum approximation and study this observable near the hum…
We complete the physical picture for the evolution of a high-energy jet propagating through a weakly-coupled quark-gluon plasma by investigating the thermalization of the soft components of the jet. We argue that the following scenario should hold: the leading particle emits a significant number of mini-jets which promptly evolve via quasi-democratic branchings and thus degrade into a myriad of soft gluons, with energies of the order of the medium temperature T. Via elastic collisions with the medium constituents, these soft gluons relax to local thermal equilibrium with the plasma over a time…
The hump-backed plateau of the single inclusive distribution of hadrons inside a jet provides a standard test of the interplay between probabilistic parton splitting and quantum coherence in QCD. The medium-induced modification of this QCD radiation physics is expected to give access to the properties of the dense medium produced in relativistic heavy ion collisions. Here, we introduce a formulation of medium-induced parton energy loss, which treats all leading and subleading parton branchings equally, and which - for showering in the vacuum - accounts for the observed distribution of soft jet…
The induced momentum spectrum of soft gluons radiated from a high energy quark propagating through a QCD medium is derived in the BDMPS formalism. A calorimetric measurement for the medium dependent energy lost by a jet with opening angle $θ_{\rm cone}$ is proposed.The fraction of this energy loss with respect to the integrated one appears to be the relevant observable.It exhibits a universal behaviour in terms of the variable $θ^2_{\rm cone} L^3 \hat q$ where $L$ is the size of the medium and $\hat q$ the transport coefficient. Phenomenological implications for the differences between cold an…
We develop a new formalism to describe the inclusive production of small radius jets in heavy-ion collisions, which is consistent with jet calculations in the simpler proton-proton system. Only at next-to-leading order (NLO) and beyond, the jet radius parameter $R$ and the jet algorithm dependence of the jet cross section can be studied and a meaningful comparison to experimental measurements is possible. We are able to consistently achieve NLO accuracy by making use of the recently developed semi-inclusive jet functions within Soft Collinear Effective Theory (SCET). In addition, single logari…
Parton branching solutions of QCD evolution equations have recently been studied to construct both collinear and transverse momentum dependent (TMD) parton distributions. In this formalism, a soft-gluon resolution scale is introduced to separate resolvable and non-resolvable branchings, and to take into account soft-gluon coherence effects. In this talk, results of fits to the high precision deep inelastic scattering (DIS) structure function measurements are shown including for the first time the effects of dynamical, i.e. branching-scale dependent, resolution scales at Next-to-Leading-Order (…
In this paper, we investigate the medium modifications of $p_{T}$ dispersion($p_{T}D$) of inclusive jets with small radius ($R=0.2$) in Pb+Pb collisions at $\sqrt{s}=2.76$~TeV. The partonic spectrum in the initial hard scattering of elementary collisions are obtained by an event generator POWHEG+PYTHIA, which matches the next-to-leading (NLO) matrix elements with parton showering, and energy loss of fast parton traversing in hot/dense QCD medium is calculated by Monte Carlo simulation within Higher-Twist formalism of jet quenching in heavy-ion collisions. We present the model calculations of n…
We consider the associated production of electroweak gauge bosons and charm or beauty quark jets at the LHC using the $k_T$-factorization framework. We apply the transverse momentum dependent (TMD) parton distributions in a proton obtained from the Parton Branching (PB) method as well as from the Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation. For the PB approach, our prescription merges the standard leading order ${\cal O}(αα_s)$ $k_T$-factorization calculations with several tree-level next-to-leading order ${\cal O}(αα_s^2)$ off-shell production amplitudes. For the CCFM scenar…
While the modification of jets by a medium as created in ultrarelativistic heavy-ion collisions is often thought of as a phenomenon affecting a hard near on-shell parton and hence treated as partonic energy loss, a more realistic view is to think of the medium effect as a relatively small correction to the Quantum Chromodynamics (QCD) vacuum radiation pattern which reduces the initial high virtuality of hard partons and leads to the development of a shower. The uncertainty relation can be used to argue that a significant part of this shower is developed even before a medium can be formed. The …
The QCD evolution of transverse momentum dependent (TMD) distribution functions has recently been formulated in a parton branching (PB) formalism. In this approach, soft-gluon coherence effects are taken into account by introducing the soft-gluon resolution scale and exploiting the relation between transverse-momentum recoils and branching scales. In this work we investigate the implications of dynamical, i.e., branching scale dependent, resolution scales. We present both analytical studies and numerical solution of PB evolution equations in the presence of dynamical resolution scales. We use …
We present an update of the branching ratios for Higgs decays in the Standard Model and the Minimal Supersymmetric extension of the Standard Model. In particular, the decays of the Higgs particles to quark and gluon jets are analyzed and the spread in the theoretical predictions due to uncertainties of the quark masses and the QCD coupling is discussed.
We calculate the decay rate of bottomonium to two-charm quark jets $Υ\to c \bar c$ at the tree level and one-loop level including color-singlet and color-octet $b \bar b$ annihilations. We find that the short distance coefficient of the color-octet piece is much larger than the color-singlet piece, and that the QCD correction will change the endpoint behavior of the charm quark jet. The color-singlet piece is strongly affected by the one-loop QCD correction. In contrast, the QCD correction to the color-octet piece is weak. Once the experiment can measure the branching ratio and energy distribu…
To investigate uncertainties in air shower simulations caused by the small-x regime, a model including leading-twist hard pQCD plus soft processes was built, which are separated by an energy dependent transverse momentum cut-off. We provide a fit of the cut-off to the total pp cross section for different PDFs using the eikonal formalism and show that for modern PDF sets there is only a small uncertainty in the mini-jet cross section, and hence in the final-state multiplicity and the number of produced muons.
We present the complete physical picture for the evolution of a high-energy jet propagating through a weakly-coupled quark-gluon plasma (QGP) by analytical and numerical investigation of thermalization of the soft components of the jet. Our results support the following physical picture: the leading particle emits a significant number of mini-jets which promptly evolve via multiple branching and thus degrade into a myriad of soft gluons, with energies of the order of the medium temperature $T$. Via elastic collisions with the medium constituents, these soft gluons relax to local thermal equili…
We propose a new method for measuring the top-quark width based on the on-/off-shell ratio of $b$-charge asymmetry in $pp\to Wbj$ production at the LHC. The charge asymmetry removes virtually all backgrounds and related uncertainties, while remaining systematic and theoretical uncertainties can be taken under control by the ratio of cross sections. Limited only by statistical error, in an optimistic scenario, we find that our approach leads to good precision at high integrated luminosity, at a few hundred MeV assuming 300-3000 fb$^{-1}$ at the LHC. The approach directly probes the total width,…
New light bosons that couple weakly to the standard model (SM) particles are predicted in various extensions of the standard model (BSM). Examples include supersymmetric (SUSY) theories with extended Higgs sectors or with a hidden valleys (dark SUSY). In these models the light bosons can be produced directly in the decay of a Higgs boson, or as part of the decay chain of SUSY particles. Depending on the branching fraction, the exotic decays of the SM-Higgs can be undetected in standard analysis techniques or due to its modified production cross section of the Higgs bosons at the LHC. Therefore…
In this paper we investigate the medium modifications of girth distributions for inclusive jets and $Z^0$ tagged jets with small radius ($R=0.2$) in Pb+Pb collisions with $\sqrt{s}=2.76$ TeV at the LHC. The partonic spectrum in the initial hard scattering of elementary collisions are obtained by a event generator POWHEG+PYTHIA, which matches the next-to-leading (NLO) matrix elements with parton showering, and energy loss of faster parton traversing in hot/dense QCD medium is calculated by Monte Carlo simulation within Higher-Twist formalism of jet quenching in heavy-ion collisions. We present …
We investigate the energy loss and equilibration of highly energetic particles/jets inside a QCD medium. Based on an effective kinetic description of QCD, including $2\leftrightarrow 2$ elastic processes, radiative $1\leftrightarrow 2$ processes, as well as the back-reaction of jet constituents onto the thermal medium, we describe the in-medium evolution of jets from the energy scale of the jet $\sim E$ all the way to the medium scale $\sim T $. While elastic processes and back-reaction are important to describe the equilibration of soft fragments of the jet, we find that the energy loss is do…
The event generator based on the higher-twist energy loss formalism -- Modular All Twist Transverse-scattering Elastic-drag and Radiation (MATTER) -- is further developed and coupled to a hydrodynamic model for studying jet modification in relativistic nuclear collisions. The probability of parton splitting is calculated using the Sudakov form factor that is constructed by a combination of vacuum and medium-induced splitting functions; and the full parton showers are simulated, including both energy-momentum and space-time evolutions of all jet partons. With the assumption that partons below a…
We propose a new phenomenological approach to establish QCD factorization of jet cross sections in the heavy-ion environment. Starting from a factorization formalism in proton-proton collisions, we introduce medium modified jet functions to capture the leading interaction of jets with the hot and dense QCD medium. A global analysis using a Monte Carlo sampling approach is performed in order to reliably determine the new jet functions from the nuclear modification factor of inclusive jets at the LHC. We find that gluon jets are significantly more suppressed due to the presence of the medium tha…
Recently the LHCb collaboration has measured both longitudinal and transverse momentum distribution of hadrons produced inside $Z$-tagged jets in proton-proton collisions at the Large Hadron Collider. These distributions are commonly referred to as jet fragmentation functions and are characterized by the longitudinal momentum fraction $z_h$ of the jet carried by the hadron and the transverse momentum $j_\perp$ with respect to the jet direction. We derive a QCD formalism within Soft-Collinear Effective Theory to describe these distributions and find that the $z_h$-dependence provides informatio…
