Recent Developments in the Lund Fragmentation Model

The production mechanism of quarkonia states in hadronic collisions is still to be understood by the scientific community. In high-multiplicity p þ p collisions, underlying event observables are of major interest. The multiparton interactions (MPIs) are underlying event observables, in which several interactions occur at the partonic level in a single p þ p event. This leads to dependence of particle production on event multiplicity. If the MPI occurs in a harder scale, there will be a correlation between the yield of quarkonia and total charged-particle multiplicity. The ALICE experiment at the LHC in p þ p collisions at ffiffi ffi s p ¼ 7 and 13 TeV has observed an approximate linear increase of relative J=ψ yield, ( dN J=ψ =dy hdN J=ψ =dyi ), with relative charged-particle multiplicity density, ( dN ch =dy hdN ch =dyi ). In our present work, we have performed a comprehensive study of the production of charmonia as a function of charged-particle multiplicity in p þ p collisions at LHC energies using the perturbative QCD-inspired multiparton interaction model, PYTHIA8 tune 4C, with and without the color reconnection scheme. A detailed multiplicity and energy-dependent study is performed to understand the effects of MPI on J=ψ production. The ratio of ψð2SÞ to J=ψ is also studied as a function of charged-particle multiplicity at LHC energies.

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“…[26,27]. After color reconnection, all the produced partons, connected with strings, fragment into hadrons via the Lund string model [28,29].…”

Section: Event Generation and Analysis Methodologymentioning

confidence: 99%

Role of multiparton interactions on J/ψ production in p+p collisions at LHC energies

Thakur

Sahoo

et al. 2018

Phys. Rev. D

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“…It incorporates a large number of hard processes, models for initial and final state parton showers, matching and merging methods between hard processes and parton showers, multiparton interactions, beam remnants, string fragmentation and particle decays. It is based on the Lund model [37]. Although most previous approaches have used cruder analytical approximations, this way of treating the quark and gluon emission is not new and was also implemented in the study of hadron production by primordial black holes: as soon as the black hole temperature becomes higher than the quantum chromodynamics (QCD) confinement scale, those processes inevitably have to be taken into account [38].…”

Section: Single Event Detectionmentioning

confidence: 99%

Phenomenology of bouncing black holes in quantum gravity: a closer look

Barrau

Bolliet

Vidotto

et al. 2016

J. Cosmol. Astropart. Phys.

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It was recently shown that black holes could be bouncing stars as a consequence of quantum gravity. We investigate the astrophysical signals implied by this hypothesis, focusing on primordial black holes. We consider different possible bounce times and study the integrated diffuse emission. I. THE MODELA new possible window for observing quantum gravitational effects has been recently pointed out in [1] (some details were refined in [2]). The idea is grounded on a result of loop cosmology [3]: when matter or radiation reaches the Planck density, quantum gravity generates a sufficient pressure to counterbalance the classically attractive gravitational force. In a black hole, matter's collapse could stop before the central singularity is formed. The standard event horizon of the black hole can be replaced by an apparent horizon [4] which is locally equivalent to an event horizon, but from which matter can eventually bounce out. The model is not specific to loop quantum gravity (for instance a similar scenario can be realized in asymptotic safety [5]). The case of non-singular black holes has been investigated by many authors [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].A heuristic description of the model we are studying can be given as follows. When the density of matter becomes high enough, quantum gravity effects generate sufficient pressure to compensate the matter's weight, the collapse ends, and matter bounces out. A collapsing "black hole" might avoid sinking into the r = 0 singularity, as much as an electron in a Coulomb potential does not sink all the way into r = 0 because of quantum mechanical effects. The picture is close to Giddings's remnant scenario [25] but with a macroscopic remnant developing into a white hole.The phenomenology associated with this scenario was considered in [26], opening the fascinating possibility to detect quantum gravity effects far below the Planck energy. It was shown there that primordial black holes (PBHs) could generate a signal in the 100 MeV range, possibly compatible with very fast gamma-ray bursts * Electronic address: aurelien.barrau@cern.ch † Electronic address: boris.bolliet@ens-lyon.fr ‡ Electronic address: fvidotto@science.ru.nl § Electronic address: celinew@kth.se [27]. Observability is made possible by the amplification due to the large ratio of the black hole lifetime over the Planck time [28].The scenario was developed in [29] with the discovery of an explicit metric satisfying Einstein's equations everywhere outside the quantum region. The model describes a quantum tunneling from a classical in-falling black hole to a classical emerging white hole. The process is seen in extreme "slow motion" from the outside because of the huge time dilatation inside the gravitational potential: this is why massive black holes would appear to us as long living black holes. Only light black holes -as primordial black holes-are expected to yield observational signatures of this model because the time required for the bounce to occur can then be sm...

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“…Note that an a priori different transverse configuration, going beyond the original Lund model, has been studied in [8] with a numerical treatment based on the ARIADNE 2 program [9]. 3 Our formalism can be easily extended to other initial conditions for τ. 4 This is also the definition of the boundaries of the sectors in Fig.…”

Section: The Minimal Surface Geometry: the Minkowskian Helicoidmentioning

confidence: 99%

“…In particular the transverse momenta are considered to be in principle randomly distributed, decor-1 By the 'conventional' Lund model we mean the original (1 + 1)-dimensional formulation not containing the extension to gluonic strings [3]. related along the chain of mesonic emissions and also uncorrelated with rapidity.…”

Section: Introductionmentioning

confidence: 99%

The Lund model at nonzero impact parameter

Janik¹,

Peschanski²

2003

Physics Letters B

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We extend the formulation of the longitudinal (1 + 1)-dimensional Lund model to nonzero impact parameter using the minimal area assumption. Complete formulae for the string breaking probability and the momenta of the produced mesons are derived using the string worldsheet Minkowskian helicoid geometry. For strings stretched into the transverse dimension, we find probability distribution with slope linear in m T similar to the statistical models but without any thermalization assumptions.

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Recent Developments in the Lund Fragmentation Model

Cited by 8 publications

References 4 publications

Role of multiparton interactions on J/ψ production in p+p collisions at LHC energies

Role of multiparton interactions on J/ψ production in p+p collisions at LHC energies

Phenomenology of bouncing black holes in quantum gravity: a closer look

The Lund model at nonzero impact parameter

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