Rencontre de Physique des Particules 2015

15 janv. 2015, 09:00 → 16 janv. 2015, 18:03 Europe/Paris

Amphi Hermite (Institut Henri Poincaré)

La Rencontre de Physique des Particules (RPP) est une manifestation annuelle des physiciens théoriciens travaillant en France dans le domaine de la physique des hautes énergies.

L'édition 2015 des Rencontres de Physique des Particules aura lieu à l'Institut Henri Poincaré à Paris  le 15 et le 16 janvier 2015.

•   •   •   •   • 

Rencontre de Physique des Particules (RPP) is an annual meeting of theoretical physicists working in France in the field of elementary particles and high energy physics.

The 2015 meeting will be held at the Henri Poincaré Institute in Paris on January 15 and 16, 2015.

 

Comité d'organisation: Damir Becirevic, Véronique Bernard, Sébastien Descotes-Genon, Emi Kou, Yann Mambrini, Bira Van Kolck, Bartjan Van Tent - LPT, IPN, LAL Orsay

jeu. 15 janvier

QCD

1 Review of Recent Developments in QCD

Orateur: Dr Gregory SOYEZ (IPhT/CEA Saclay)

Transparents 1-Soyez.pdf

2 Small radius jets to all orders

As hadron collider physics continues to push the boundaries of precision, it becomes increasingly important to have methods for predicting properties of jets across a broad range of jet radius values R, and in particular for small R. In this presentation we will start with a brief review of jet physics at hadron colliders, and introduce a method to resum all leading logarithmic terms, $\alpha_s \ln R$, in the limit of small R, for a wide variety of observables. These include the inclusive jet spectrum, jet vetoes for Higgs physics and jet substructure tools. We will examine and comment on the underlying order-by-order convergence of the perturbative series for different R values.

Orateur: M. Frédéric Dreyer (LPTHE)

Transparents 2-Dreyer.pdf

3 Impact factor for high-energy two and three jets diffractive production

We present the calculation of the impact factor for the photon to quark, antiquark and gluon transition within Balitsky's high energy OPE. We also rederive the impact factor for photon to quark and antiquark transition within the same framework. These results provide the necessary building blocks for further phenomenological studies of inclusive diffractive DIS as well as for two and three jets diffractive production which go beyond approximations discussed in the litterature.

Orateur: M. Renaud Boussarie (LPT Orsay)

Transparents 3-Boussarie.pdf

4 Universality of perturbative QCD soft radiation in ee, ep, and pp collisions

Soft radiation consists of coherent low energy gluons that interact with initial and final state jets at wide angles from the jet axis, and we show that this soft radiation in ee, ep and pp collisions is universal to order $\alpha_s^2$ in perturbation theory. We factor this soft radiation out of the multi-scale cross-section using Soft Collinear Effective Theory, which is an effective field theory of QCD for processes with high energy, light-like degrees of freedom interacting via soft degrees. The universality of soft radiation suggests that low energy QCD radiation is independent of the process and can be decoupled from the high-energy, short-distance jet structure.

Orateur: Ou Zhang (University of Arizona and IPN-Orsay)

Transparents 4-Zhang.pdf

5 J/psi-Pair Production at Large Momenta: Indications for Double-Parton Scatterings and Large alpha_s^5 Contributions

The recent observations of prompt $J/\psi$-pair production by CMS at the LHC and by D0 at the Tevatron reveal the presence of different production mechanisms in different kinematical regions. We find out that next-to-leading-order single-parton-scattering contributions at $\alpha_s^5$ dominate the yield at large transverse momenta of the pair. Our analysis further emphasises the importance of double-parton-scatterings --which are expected to dominate the yield at large rapidity differences-- at large invariant masses of the pair in the CMS acceptance. In addition, we provide the first exact --gauge-invariant and infrared-safe-- evaluation of a class of leading-$P_T$ next-to-next-to-leading-order contributions, which are dominant in the region of large sub-leading transverse momenta, precisely where the colour-octet contributions can be non-negligible. Finally, we discuss the contribution from decays of excited charmonium states within both single- and double-parton scatterings and suggest measurements to distinguish them.

Orateur: Dr Hua-Sheng Shao (CERN)

Transparents 5-Shao.pdf

6 Quarkonia suppression in a quark-gluon plasma produced in heavy ion collisions at high energies.

The theory of elementary particles predicts the existence of a new state of matter: the Quark-Gluon Plasma (QGP). The latter may have existed at the first moments of the Universe following the Big Bang and can be, in theory, re-produced in heavy ion collisions at high energy colliders (e.g. the LHC). One of the QGP possible observables is the suppression of the quarkonia (heavy quark/antiquark bound states), i.e. a characteristic decrease of the their detected amount in comparison to proton-proton collisions, in which no QGP production is possible. This suppression has indeed been observed, but the latest observations expose a puzzling saturation of the suppression when the collision energy increases. A dynamical scenario is proposed to describe these kinetic dependences.

Orateur: M. Roland Katz (Subatech)

Transparents 6-Katz.pptx

10:35 Pause café / Coffee Break

QCD-2

7 Describing hadron structure using Dyson-Schwinger equations

If at high energy QCD can be described using perturbation theory due to asymptotic freedom, when going at low energy the fundamental degrees of freedom of the theory, quarks are gluons, are bounded inside hadrons. The hadron structure in terms of partons has been studied since the 1960s. Today several objects have been both theoretically and experimentally studied, like for instance Generalized Parton Distributions (GPDs) which contains a three dimensional information about the parton structure of hadrons. However, it is still not possible to compute such objects directly from QCD first principles. As a first step toward this ideal goal, we have developed here a model for the pion GPD based on the Dyson-Schwynger equations, which are a way to compute QCD non pertubative Green functions. We have successfully compared our model with available experimental data of pion form factor and pion Parton Distribution Function (PDF), and managed to sketch the partonic 3D structure of the pion.

Orateur: M. Cédric Mezrag (IRFU/SPhN)

Transparents 3-Boussarie.pdf

8 Octet baryon masses in covariant baryon chiral perturbation theory

We study the ground-state octet baryon masses and sigma terms using the covariant baryon chiral perturbation theory (ChPT) with the extended-on-mass-shell (EOMS) renormalization scheme up to next-to-next-to-next-to-leading order (N$^3$LO). In order to systematically study the lattice QCD data and to fix the low-energy constants (LECs), the finite-volume corrections (FVCs) and finite lattice spacing discretization effects of LQCD simulations are included self-consistently. Through a simultaneous fit of all the publicly available $n_f = 2+1$ lattice QCD data from the PACS-CS, LHPC, HSC, QCDSF-UKQCD and NPLQCD collaborations, it shows that the N$^3$LO EOMS BChPT can give a reasonable fit with $\chi^2/\mathrm{d.o.f.} = 1.0$ and the various lattice simulations seem to be consistent with each other. We also conclude that the finite lattice spacing discretization effects up to $\mathcal{O}(a^2)$ can be safely ignored. Finally, the octet baryon sigma terms are predicted via the Feynman-Hellmann theorem. In particular, the pion- and strangeness-nucleon sigma terms are $\sigma_{\pi N} = 55(1)(4)$ MeV and $\sigma_{sN} = 27(27)(4)$ MeV, respectively.

Orateur: M. Xiu-Lei REN (IPN Orsay)

Transparents 2-Ren.pdf

9 Ab-initio calculation of the neutron-proton mass difference

The difference between the masses of the neutron and the proton is only 0.14% of their average. Yet this difference has important implications for the existence and stability of ordinary matter. After explaining how electromagnetic and mass isospin breaking effects can be included in lattice QCD computations, I will show how this mass difference arises from a subtle cancellation of these two effects. I will also report on results for splittings in the $\Sigma$, $\Xi$, $D$ and $\Xi_{cc}$ isospin multiplets, some of which are predictions. As will be explained, the results are obtained from an ab-initio calculation in full lattice QCD plus QED, that includes the effects of non-degenerate up, down, strange and charm quarks in the sea.

Orateur: Laurent Lellouch (CPT Marseille)

Transparents 3-Lellouch.pdf

10 Pion couplings to the scalar B meson

Computing the quark propagator on the lattice gets more and more difficult as the light quark becomes small and approach its physical value. Therefore, most simulations are performed at unphysical light quark masses and the results are extrapolated to the physical mass using fit formulae inspired by chiral perturbation theory. In the case of heavy-light mesons, one can use the Heavy Meson Chiral Perturbation Theory parametrized, at leading order, by three couplings $g$, $\tilde{g}$ and $h$. In this talk, I will present a lattice computation of the couplings $\tilde{g}$ and $h$ which appear when positive parity states are taken into account. In particular, I will show that the coupling $h$ is large and cannot be neglected in chiral loops. The lattice simulations are performed on a set of $N_f = 2$ dynamical quarks configurations made available by the Lattice Coordinated Simulations effort.

Orateur: Antoine Gérardin (Laboratoire de Physique Corpusculaire (LPC))

Transparents rpp_gerardin.pdf

11 Random Matrix Theory for Wilson-Dirac Operator

We summarize recent analytical results obtained for the discretization effects of the non-Hermitian Wilson Dirac operator. We include the effect of all three leading low energy constants in our analysis. In particular we discuss the results for the eigenvalue densities close to the continuum limit but we also consider the case of large lattice spacing which is closely related to the mean field limit. Finally, we extract simple relations between measurable spectral quantities and the low energy constants. These relations serve as a new way to measure the additional low energy constants of Wilson chiral perturbation theory.

Orateur: Savvas Zafeiropoulos (Goethe Universitaet Frankfurt)

Transparents RPP15_Zafeiropoulos.pdf

12 Characterizing New physics with Polarized Beams at High-Energy Hadron Colliders

## Motivations ## - Status of New Physics searches at the LHC - Why using polarized beams for New Physics searches? - Future Accelerators & Polarized beams ## Physics at polarized hadron colliders ## - Polarized Parton Distribution Functions - Parton luminosities & cross sections - Longitudinal spin asymmetries ## Physics case: Monotop signature ## - Monotop production in the Standard model - Monotop production in the RPV-MSSM - Monotop production in the Hylogenesis model - Monotop production in the X-model ## Conclusions ##

Orateur: Josselin Proudom (LPSC)

Transparents RPP-2015_proudom.pdf

13 Magnetic Wilson loops in the classical field of high-energy heavy-ion collisions

The field configuration in the first moments of high-energy heavy-ion collisions is represented by strong longitudinal chromo-electric and chromo-magnetic fields. The form of these fields is obtained by solving the classical Yang-Mills equations of motion for two color charge sheets passing through each other with appropriate boundary conditions on the light cone. We calculate perturbatively the expectation value of the magnetic Wilson loop operator in the first moment of the collision. For the magnetic flux we obtain a first non-trivial term that is proportional to the square of the area of the loop. The result agrees with numerical calculations for small area loops. Screening effects are not present in the analytical calculation. A numerical result for larger loops gives an area law behavior of the flux, which indicates existence of independent magnetic vortices over distance scales up to few times the inverse saturation scale.

Orateur: Elena Petreska (CPHT - Ecole Polytechnique)

Transparents 7-Petreska.pdf

Posters [exhibited during the Rencontre]

14 Effect of Degenerated Particles on Internal Bremsstrahlung of Majorana Dark Matter

Gamma-ray generated by annihilation or decay of dark matter can be its smoking gun signature. In particular, gamma-ray coming from internal bremsstrahlung of dark matter is promising since it can be a leading emission of sharp gamma-ray. However if thermal production of Majorana dark matter is considered, the derived cross section for internal bremsstrahlung becomes too small to be observed by future gamma-ray experiments. We consider a framework to achieve an enhancement of the cross section by taking into account degenerated particles with dark matter. We find that the enhancement of about order one is possible without conflict with the dark matter relic density. Due to the enhancement, it would be tested by the future experiments such as GAMMA-400 and CTA.

Orateur: Dr Takashi Toma (LPT Orsay)

15 Fluctuation signatures of the QCD critical point

Locating the QCD critical point is the goal of several major heavy ion collision experiments, and it may be possible to see signatures of critical behaviour in event-by-event fluctuations of conserved charges. We show characteristic peaks in the third $\chi_3$ and fourth $\chi_4$ fluctuation moments of baryon number as a function of chemical potential (or center of mass energy) and how they depend on proximity of freeze out to the critical point. In a model independent analysis, we explain qualitative features of the moments' dependence on chemical potential and temperature near the critical point, and we identify a few signatures, such as relative location of the $\chi_3$ and $\chi_4$ peaks, expected to be robust. Using the Gross Neveu model we provide a quantitative example of these predictions, which may support experimental observations of a peak in $\chi_4$ as a signature of the critical point.

Orateur: Dr Lance Labun (University of Texas, Austin)

16 Generating X-ray lines from annihilating dark matter

Orateur: M. Lucien Heurtier (CPHT, Ecole Polytechnique)

17 Harnessing astrophysical uncertainties in the direct detection of dark matter

In order to analyse data from direct detection experiments, it has previously been necessary to make assumptions about the dark matter (DM) speed distribution. However, it has been shown that for a future discovery, poor astrophysical assumptions may lead to a bias in the reconstructed DM mass and cross section. I will present a completely general parametrisation of the speed distribution which allows an unbiased measurement of the DM mass and, when combined with neutrino telescope data, of the DM cross section. As an added bonus, the method can be used to reconstruct the distribution function itself from future data, allowing us also to probe the dynamics and formation history of the Milky Way.

Orateur: Dr Bradley Kavanagh (IPhT Saclay)

18 Interpreting LHC searches for new physics with SModelS

SModelS is an automatised public tool for the interpretation of so-called Simplified Model Spectra (SMS) results from the LHC. I will discuss the working principle of SModelS and present some applications to supersymmetric models.

Orateur: Sabine Kraml (LPSC Grenoble)

19 Lattice computation of the nucleon sigma terms

Besides connecting the pion-nucleon and the kaon-nucleon amplitudes to the hadron spectrum, nucleon sigma terms play an important role in the direct detection of Dark Matter. A lattice computation will be outlined, preliminary results for the up-down and strange sigma terms will be presented and strategies to improve on their precision will be illustrated.

Orateur: Dr Christian Torrero (Centre de Physique Théorique (Université d'Aix-Marseille))

20 Multi-tops at the LHC

One of the most interesting sectors to look for new physics at the LHC is that of the top quark, both for theoretical and phenomenological reasons. A number of possible final states involving the top have been considered by the experimental collaborations and they have successfully constrained many Beyond the Standard Model scenarios. In this presentation, I will describe a study intended to address the question of how the occurrence of much more exotic final states, namely many-top events, can be constrained using existing analyses, and whether they could be improved using a different selection procedure. I will show that current data allows to put constraints on the production of six-top final states in a toy model created for the purpose of studying this signature and that this is the multiplicity limit one can hope to reach with Run 1.

Orateur: M. Nicolas Deutschmann (IPNL)

21 Off-shell and on-peak measurements intertwined

As the LHC experimental collaborations have released results about the influence of the existence of the Higgs boson outside of its mass shell, interpreting it as a constraint on its total width, we propose a more model-independent way to recast these observations. We advocate for the use of the parametrisation previously introduced in hep-ph:0901.0927 and hep-ph:1210.8120 to use conjointly on-peak and off-shell measurements. Using a simple toy-model, we show that a degeneracy existing on-peak in the parameters can be lifted by also including off-shell data.

Orateur: Jean-Baptiste Flament (IPNL)

22 On the CP-odd Higgs boson

Orateur: M. Olcyr De Lima Sumensari

Flavor Physics

23 Quark Flavor (Review)

Orateur: Dr Jérôme CHARLES (CPT Marseille (UMR 7332))

Transparents rpp_charles.pdf

24 Lepton Flavor (Review)

Orateur: Dr Michele Frigerio (Laboratoire Charles Coulomb, CNRS)

Transparents RPP-2015-_Frigerio.pdf

25 Lepton flavour violating lepton decays in the inverse seesaw: SUSY and non-SUSY contributions

In previous works (JHEP03(2012)100, JHEP09(2012)015), we have highlighted that the Higgs and Z-mediated penguin diagrams contributing to lepton flavour violating (LFV) observables like $\tau \rightarrow \mu \mu \mu$ are strongly enhanced in the supersymmetric inverse seesaw model. It has recently been pointed out (Phys.Rev.D90(2014)013008) that an error in the literature for the Z-penguins form factors would lead to a non-physical non-decoupling behaviour. This work (JHEP11(2014)048) is devoted to the study of LFV lepton decays and $\mu - e$ conversion in the supersymmetric inverse seesaw, taking all contributions into account with the corrected form factors. We explicitly distinguish various regimes depending on the dominant contribution and give predictions for various observables, some of them already within reach of the current experiments.

Orateur: Dr Cedric Weiland (IFT UAM/CSIC)

Transparents RPP2015_Weiland.pdf

26 Constraining the Doublet Left-Right Model

Left-Right Models (LRM) attempt at giving an understanding of the violation of parity (or charge-conjugation) by the weak interactions in the SM through a similar description of left- and right-handed currents at high energies. The spontaneous symmetry breaking of $ SU(2)_L \times SU(2)_R \times U(1)_{(B-L)} $ is usually triggered by an enlarged Higgs sector, usually consisting of two triplet fields (left-right symmetry breaking) and a bi-doublet (electroweak symmetry breaking). I reconsider an alternative LRM with doublet instead of triplet fields. After explaining some features of this model, I discuss constraints on its parameters using electroweak precision observables (combined using the CKMfitter frequentist statistical framework) and neutral-meson mixing observables.

Orateur: M. Luiz Henrique Vale Silva (LPT)

Transparents RPP2015.pdf

27 Kaon phenomenology, Delta I=1/2 rule and BSM kaon oscillations

Kaon physics provides us with highly-non trivial tests of the Standard Model and is a rich source of information for Beyond the Standard Model (BSM) phenomenology. CP violation is among the most intriguing phenomena in particle physics and is very well measured in kaon decays, but a complete and quantitative theoretical prediction is still missing. However, the RBC-UKQCD collaborations have made tremendous progress in the last few years toward the computation of the $K\to \pi\pi$ amplitudes. I will present our work, including our new data points with physical quark masses. From our results, I will show a possible explanation of the $\Delta I = 1/2$ rule. Finally, I will present our work on neutral kaon mixing, including the BSM contribution and the constraints it implies on the scale of new-physics.

Orateur: Dr Nicolas Garron (University of Cambridge)

Transparents garron.pdf

15:35 Pause café - Coffee Break

Table Ronde organisée par le BTP2

28 Slides_BTP2

Orateur: Prof. Aldo Deandrea (IPNL)

Transparents BTP2.pdf

29 Université

Orateur: Jean Orloff (LPC Clermont, Univ. Blaise Pascal)

Transparents CNU29@RPP2015.pdf

30 Minutes - TABLE RONDE 2015

Orateur: Prof. Aldo Deandrea (IPNL)

Transparents Table_ronde_RPP2015.pdf

ven. 16 janvier

Higgs Physics and New Physics Scenarios

31 Higgs and New Physics

Orateur: Prof. Fawzi Boudjema (LAPTH)

Transparents Boudjema.pdf

32 Searching for the Higgs bosons of the NMSSM

The search for signs of more scalars is a primary task of current and future experiments. In particular, in the next-to-minimal supersymmetric Standard Model, the extra Higgs bosons could well be the lightest new particles around. I will outline a possible overall strategy to look for the extra CP-even scalars, comparing the impact of measurements of the SM Higgs couplings with the direct searches of the new states, at current and future facilities. In doing so, I will rely on an analytical understanding of the Higgs system, to keep under control the complications due to the proliferation of model parameters.

Orateur: Filippo Sala (IPhT CEA-Saclay)

Slides FSala_RPP.pdf

33 A Light Singlet in Gauge Mediation

I will discuss the possibility of a light supersymmetric singlet below 100 GeV in the context of a very predictive model that combines the NMSSM and Gauge Mediation. This model has been originally proposed by Delgado,Giudice and Slavich, but the LEP bound had been imposed on the lightest Higgs state. We re-analyzed this model and found new interesting regions in the parameter space with a light singlet state that mixes with the SM-like Higgs at 125 GeV. This mixing is small enough to evade LEP and LHC constraints, but large enough to give a substantial contribution to the tree-level Higgs mass, thus reducing the required mass scale of supersymmetric particles. Essentially only a single parameter is left undetermined that controls the gravitino phenomenology and can lead to novel collider signatures.

Orateur: Robert Ziegler (LPTHE)

Slides Ziegler.pdf

34 Bridging Composite Higgs and Technicolor with Higgs data

We focus on the possibility that the Higgs boson is a state which is either as a Pseudo Goldstone Boson of an effective Lagrangian description or as a composite state made of techini fermions. In this composite Higgs model, the symmetry breaking pattern is SU(4)/SP(4) and the light Higgs will further mix with a heavier techni-Higgs. We consider the constraints on the parameter space both from the Higgs coupling measurements and the EW precision test and mainly discuss the phenomenology related to the eta particle as well as the heavier Higgs.

Orateur: Dr Haiying CAI (IPNL, Lyon)

Transparents HCai.pdf

35 Light-by-light scattering with intact protons at the LHC: from Standard Model to New Physics

We discuss the discovery potential of light-by-light scattering at the LHC, induced by the SM and by new exotic charged particles. Our simulation relies on intact proton detection in the planned forward detectors of CMS and ATLAS. The full four-photon amplitudes generated by any electrically charged particles of spins 1/2 and 1, including the SM processes involving loops of leptons, quarks and W bosons are implemented in the Forward Physics Monte Carlo generator. Our method provides model-independent bounds on massive charged particles, only parametrized by the spin, mass and "effective charge" Qeff of the new particle. We also discuss the sensitivities to neutral particles such as a strongly-interacting heavy dilaton and warped Kaluza-Klein gravitons, whose effects could be discovered for masses in the multi-TeV range.

Orateur: Dr sylvain fichet (ICTP/SAIFR)

Slides FICHET_RPP_15.pdf

36 EFT analysis of New Physics searches: from neutrons to Higgses

EFTs are a useful tool to analyze and compare different New Physics searches. I'll discuss the interplay between low-energy beta decay experiments and LHC searches, the application to Higgs decay data and the limitations of the method when light new particles are present.

Orateur: Martin Gonzalez-Alonso (IPN Lyon)

Transparents RPP2015_final.pdf

10:35 Pause café - Coffee Break

Dark Matter - Astroparticles

37 Current aspects of Dark Matter

I briefly discuss the current status of dark matter phenomenology, with an emphasis on simple (or simplified) models and their possible experimental signatures.

Orateur: M. Michel Tytgat (ULB)

Transparents RPP_Tytgat.pdf

38 The gamma-ray excess at the Galactic Center and the antiproton constraints.

A GeV gamma-ray excess has possibly been individuated in Fermi-LAT data from the Galactic Center and interpreted in terms of Dark Matter annihilations, either in hadronic or leptonic channels. In order to test this tantalizing interpretation, we address two issues: (i) we improve the computation of secondary emission from DM, confirming it to be very relevant for determining the DM spectrum in the leptonic channels, (ii) we consider the constraints from antiprotons on the DM hadronic channel, finding that the uncertainties on the propagation model and the solar modulation play a major role. The limits that we obtain severely constrain the DM interpretation of the excess in the hadronic channel, for standard assumptions on the Galactic propagation parameters and solar modulation. However, they considerably relax if more conservative choices are adopted.

Orateur: Marco Taoso (IPhT Saclay/CEA)

Transparents MTaoso_RPP.pdf

39 Dark portal scenarios

We analyze some simple but general scenarios in which the interactions of a (fermionic) Dark Matter with Standard Model particles are mediated by a scalar/pseudoscalar or vector state. We discuss the impact of current Dark Matter searches, with particular focus on the interpretation of the recently reported gamma-ray excess. We will also illustrate the prospect of detection in next future experiments.

Orateur: Dr Giorgio Arcadi (LPT Orsay)

Transparents RPP_arcadi.pdf

40 Is Coy dark matter really coy?

.

Orateur: Dr Chiara Arina (IAP)

Transparents talk_CArina.pdf

41 The Dark Side of Naturalness Beyond the MSSM

Direct searches of neutralino dark matter in underground scattering experiments constitute a significant pressure on weak scale naturalness in the MSSM. The resulting neutralino fine-tuning is almost as severe as that arising from the heavy stops required by a125GeV Higgs boson. We analyse in an effective field theory framework the implication for neutralino fine-tuning of MSSM extensions which solve the little hierarchy problem of the Higgs mass through the introduction of a heavy, non-decoupled supersymmetric sector. We argue that in these models the neutralino fine-tuning is parametrically worse than in the MSSM for gaugino dark matter. Thermally produced Higgsino dark matter typically displays a comparable level of fine-tuning with the noteworthy exception of dark matter below the WW annihilation threshold. This light Higgsino scenario is only mildly fine-tuned and, in contrast with the MSSM, it does not conflict with the LEP bound on chargino. Any improvement on either charged higgsino searches or direct dark matter detection would test this scenario.

Orateur: Dr Cedric Delaunay (LAPTH)

Transparents darkBMSSM_delaunay_rpp2015.pdf

42 Dark matter effective field theory at present and future colliders

The absence of BSM signals at the Large Hadron Collider and the strong cosmological evidence for dark matter (DM) have motivated a fairly model-independent Effective Field Theory (EFT) approach to describe the interactions of DM particles with the Standard Model. This approach is known to be both powerful, thanks to its simplicity, as well as subtle, due to its potential limitations. I will discuss up-to-date constraints on the corresponding effective operators coming from direct DM searches, the LHC and cosmic DM abundance measurements. I will moreover present relevant predictions for the reach of the next LHC run as well as that of a futuristic 100 TeV hadron collider and discuss the validity of the EFT description in the corresponding experimental environments.

Orateur: Dr ANDREAS GOUDELIS (HEPHY - Vienna)

Transparents AndreasRPP2015.pdf

Cosmology

43 Review Talk

Orateur: Dr Filippo Vernizzi (IPhT - CEA Saclay)

Transparents Vernizzi_RPP2015.pdf

44 Hawking radiation in laboratory analogues

Hawking radiation, despite being known to theoretical physics for 40 years, remains an elusive phenomenon. It also suffers, in its original context of gravitational black holes, from practical and conceptual difficulties. In order to gain better theoretical understanding and, it is hoped, experimental verification of Hawking radiation, much study is being devoted to laboratory systems which use moving media to model the spacetime geometry of black holes. I shall briefly describe the analogy between black holes and moving media, and show how it can shed new light on the seemingly exotic phenomenon of Hawking radiation.

Orateur: Dr Scott Robertson (LPT Orsay)

Transparents RPP_Robertson.pdf

45 On pair-instability Supernovae explosions

According to theoretical models, massive stars with masses within the 100- 250 solar mass range should explode as pair-instability supernovae (PISNe). Since the first stars of the Universe are believed to be very massive, these supernovae should play a signicant role in the early stages of its history. But these stars represent the last unobserved population, owing to detection limits of current telescopes. In this presentation, we analyze pair-instability supernovae explosions using various numerical codes. We evolve series of the congurations of oxygen cores to establish a range of masses and initial conditions where this type of explosion is possible. We also study the role of possible instabilities in the propagation of shockwaves during the last stage of the explosion. This investigation could help us to predict the observational properties of PISNe for future space and ground telescopes and the possible connections with Gamma-Ray Bursts.

Orateur: Prof. Pascal Chardonnet (Université de Savoie/LAPTH)

Transparents RPP2015-Chardonnet.pdf

46 Non relativistic Operators in Direct Dark Matter Searches

Orateur: Dr Paolo Panci (Institut d'Astrophysique de Paris)

Transparents Panci_RPP_2015.pdf

47 A new look at the cosmic ray positron fraction.

The positron fraction in cosmic rays has been recently measured with improved accuracy up to 500 GeV by the space-borne experiment AMS-02, and it was found to be a steadily increasing function of energy, above 10 GeV. This behaviour is in tension with standard astrophysical mechanisms, in which positrons are secondary particles, produced in the interactions of primary cosmic rays during their propagation in the interstellar medium. The observed anomaly in the positron fraction triggered a lot of excitement, as it could be interpreted as an indirect signature of the presence of dark matter species in the Galaxy -- the so-called weakly interacting massive particles or WIMPs. Alternatively, it could be produced by nearby astrophysical sources, such as pulsars.

Orateur: M. Mathieu Boudaud (LAPTh)

Transparents RPP_2015_M.Boudaud.pdf

48 Making sense of the local Galactic escape speed estimates in direct dark matter searches

The knowledge of the high velocity tail of the WIMP velocity distribution function has a strong impact on the way direct detection (DD) may constrain or discover light WIMPs in the GeV mass range. Recently, there have been important observational efforts to estimate the so-called Galactic escape speed at the position of the Earth, like for instance the analysis published in early 2014 by the RAVE Collaboration (Piffl et al., 2014), which is of interest in the perspective of reducing the astrophysical uncertainties in DD. Nevertheless, these new estimates cannot be used blindly as they rely on assumptions in the dark halo modelling, which induce tight correlations between the escape speed and other local astrophysical parameters (circular velocity, dark matter density, distance to the Galactic center). We make a self-consistent study of the implications of the RAVE results on DD assuming isotropic DM velocity distributions, both Maxwellian and ergodic. Taking as reference the experimental sensitivities currently achieved by LUX, CRESST2, and SuperCDMS, we show that the uncertainties inferred for the exclusion curves in the low WIMP mass region are moderate. We discuss the level of (dis)agreement of these results with other independent astrophysical constraints.

Orateur: M. Stefano Magni (Université Montpellier 2)

Transparents TalkRPP2015SMagni.pdf

15:35 Pause café - Coffee Break

New Theoretical Developments

49 Recent developments in formal high energy physics

I will review several recent important developments in high energy physics, including: -Perturbative and non-perturbative results in supersymmetric non-abelian gauge theories (AdS / CFT, Localisation, non-Langrangian theories). -Superstring and supergravity amplitudes, 3-loop amplitude in string theory, color kinematic duality and double copy, BMS symmetry and infrared behaviour. -Black hole information paradox, Mathur conjecture and exact counting through localisation.

Orateur: Dr Guillaume Bossard (CPhT)

Transparents BossardReview.pdf

50 Renormalization Group Flows for Quantum Gravity

We shall review briefly some current approaches to quantum gravity, focusing in particular on the recent progress on tensor-based models which sum over all discretized space-time geometries and can be shown renormalizable and asymptotically free.

Orateur: Prof. Vincent RIVASSEAU

Transparents PhysPartIHPJan2015.pdf

51 Renormalization Group Optimized Perturbation: some illustrations at zero and finite temperature.

We discuss our recently developed variant of the so-called optimized perturbation (OPT), 'RGOPT', consistently resumming renormalization group dependence generically for zero or finite temperature theories. It is illustrated with a rather precise determination of 1) the QCD basic scale and coupling from the pion decay constant $F_\pi$: $\alpha_S(m_Z)[\overline{MS}] \simeq 0.1174 \pm 0.002$; 2) the quark condensate $<\bar q q>$ in the chiral limit. 3) At finite temperature the pressure for the illustrative $\phi^4$ model is calculated to second (modified perturbation) order. Our method and results differ sharply from other similar resummation approaches, in particular the notoriously bad stability and scale dependence of thermal perturbative expansions for moderately large coupling is shown to drastically improve, with anticipated similar properties in thermal QCD.

Orateur: Jean-Loic Kneur (LCC Montpellier)

Transparents kneur_rpp15.pdf

52 From OPE to Soft-Wall

We will show how it is possible to implement a chiral symmetry breaking mechanism in soft-wall model of holographic QCD. By perturbing a dilaton potential, we show also that it is possible to reproduce the exact Operator Product Expansion and the spectrum of the vector-vector and axial-axial correlators in the Large-N$_c$ limit.

Orateur: Dr David Greynat (Universita di Napoli and INFN)

Transparents Greynat_RPP15.pdf

53 Nonrenormalizablity of nonequilibrium quantum field theory in the classical approximation

Nonequilibrium quantum field theory in the classical statistical approximation (CSA) has a broad range of applications to understanding thermalization of systems with a large occupation number both in cosmology and in ultra-relativistic heavy-ion collisions. In my talk, I would like first to give a brief introduction to the CSA in the $g^2\phi^4$ theory. Then, I will present our discovery of nonrenormalizability of such an approximation (Phys. Rev. D 90, 065029 (2014)). I shall also show the Boltzmann equation in two types of classical approximations, which are equivalent to the CSA in the case that the distribution function $f$ satisfies $\frac{1}{g^2}\gg f\gg 1$. The numerical results to the Boltzmann equation in one of the classical limits presented in another paper of ours (arXiv:1409.0701, to appear in PRD) further confirm nonrenormalizability of the CSA. Besides, I would also like to discuss the features of forming a Bose-Einstein condensate in the classical approximations.

Orateur: Dr Bin Wu (IPhT, CEA/Saclay)

Transparents WU_RPP2015.pdf