Probing the scale of New Physics at the LHC: the example of Higgs data

We present a technique to determine the scale of New Physics (NP) compatible with any set of data, relying on well-defined credibility intervals. Our approach relies on the statistical view of the effective field theory capturing New Physics at low energy. We introduce formally the notion of testable NP and show that it ensures integrability of the posterior distribution. We apply our method to the Standard Model Higgs sector in light of recent LHC data, considering two generic scenarios. In the scenario of democratic higher dimensional operators generated at one-loop, we find the testable NP scale to lie within $[10,260]$ TeV at $95\%$ Bayesian credibility level. In the scenario of loop-suppressed field strength-Higgs operators, the testable NP scale is within $[28,1200]$ TeV at $95\%$ Bayesian credibility level. More specific UV models are necessary to allow lower values of the NP scale.Comment: 19 pages, 3 figures, cosmetic changes, matches journal version. Nuclear Physics B (2014

Taming systematic uncertainties at the LHC with the central limit theorem

We study the simplifications occurring in any likelihood function in the presence of a large number of small systematic uncertainties. We find that the marginalisation of these uncertainties can be done analytically by means of second-order error propagation, error combination, the Lyapunov central limit theorem, and under mild approximations which are typically satisfied for LHC likelihoods. The outcomes of this analysis are i) a very light treatment of systematic uncertainties ii) a convenient way of reporting the main effects of systematic uncertainties such as the detector effects occuring in LHC measurements.Comment: 16 pages, 2 figures. v3: Minor changes. NPB versio

Shining Light on Polarizable Dark Particles

We investigate the possibilities of searching for a self-conjugate polarizable particle in the self-interactions of light. We first observe that polarizability can arise either from the exchange of mediator states or as a consequence of the inner structure of the particle. To exemplify this second possibility we calculate the polarizability of a neutral bosonic open string, and find it is described only by dimension-8 operators. Focussing on the spin-0 case, we calculate the light-by-light scattering amplitudes induced by the dimension-6 and 8 polarizability operators. Performing a simulation of exclusive diphoton production with proton tagging at the LHC, we find that the imprint of the polarizable dark particle can be potentially detected at 5$\sigma$ significance for mass and cutoff reaching values above the TeV scale, for $\sqrt{s}=$13~TeV and 300 fb$^{-1}$ of integrated luminosity. If the polarizable dark particle is stable, it can be a dark matter candidate, in which case we argue this exclusive diphoton search may complement the existing LHC searches for polarizable dark matter.Comment: 24 pages, 3 figures. v2: Comments added. Analysis of intrinsic polarizability modified, conclusions unchanged. Matches JHEP versio

The SUSY flavor problem in 5D GUTs

In 5D SUSY GUTs, wave-function localization permits to reproduce flavour hierarchy. As this mechanism also acts on SUSY breaking parameters, it can potentially solve the SUSY flavour problem. We carry out an analysis of the Holographic Grand Unification framework, where we take properly into account effects of matrix anarchy. In this contribution, we focus on brane-localized SUSY breaking and its consequences.Comment: Prepared for the proceedings of the Moriond 2011 EW session. 4 pages, 7 figure

New likelihoods for shape analysis

We introduce a new kind of likelihood function based on the sequence of moments of the data distribution. Both binned and unbinned data samples are discussed, and the multivariate case is also derived. Building on this approach we lay out the formalism of shape analysis for signal searches. In addition to moment-based likelihoods, standard likelihoods and approximate statistical tests are provided. Enough material is included to make the paper self-contained from the perspective of shape analysis. We argue that the moment-based likelihoods can advantageously replace unbinned standard likelihoods for the search of non-local signals, by avoiding the step of fitting Monte-Carlo generated distributions. This benefit increases with the number of variables simultaneously analyzed. The moment-based signal search is exemplified and tested in various 1D toy models mimicking typical high-energy signal--background configurations. Moment-based techniques should be particularly appropriate for the searches for effective operators at the LHC.Comment: 23 pages, 5 figure

Effective theory for neutral resonances and a statistical dissection of the ATLAS diboson excess

We classify the complete set of dimension-5 operators relevant for the resonant production of a singlet of spin 0 or 2 linearly coupled to the Standard Model (SM). We compute the decay width of such states as a function of the effective couplings, and provide the matching to various well-motivated New Physics scenarios. We then investigate the possibility that one of these neutral resonances be at the origin of the excess in diboson production recently reported by the ATLAS collaboration. We perform a shape analysis of the excess under full consideration of the systematic uncertainties to extract the width $\Gamma_{\rm tot}$ of the hypothetical resonance, finding it to be in the range 26 GeV $<\Gamma_{\rm tot}<$ 144 GeV at 95\% C.L. We then point out that the three overlapping selections $WW$, $WZ$, $ZZ$ reported by ATLAS follow a joint trivariate Poisson distribution, which opens the possibility of a thorough likelihood analysis of the event rates. The background systematic uncertainties are also included in our analysis. We show that the data do not require $W\!Z$ production and could thus in principle be explained by neutral resonances. We then use both the information on the width and the cross section, which prove to be highly complementary, to test the effective Lagrangians of singlet resonances. Regarding specific models, we find that neither scalars coupled via the Higgs-portal nor the Randall-Sundrum (RS) radion can explain the ATLAS anomaly. The RS graviton with all matter on the infrared (IR) brane can in principle fit the observed excess, while the RS model with matter propagating in the bulk requires the presence of IR brane kinetic terms for the gauge fields.Comment: 31 page

Anomalous gauge interactions in photon collisions at the LHC and the FCC

The forward proton detectors recently installed and operating at the LHC open the possibility to observe photon collisions with high precision, providing a novel window on physics beyond the Standard Model. We review recent simulations and theoretical developments about the measurement of anomalous ${\gamma}{\gamma}{\gamma}{\gamma}$ and $Z{\gamma}{\gamma}{\gamma}$ interactions. The searches for these anomalous gauge interactions are expected to set bounds on a wide range of particles including generic electroweak particles, neutral particles with dimension-5 coupling to gauge bosons, polarizable dark particles, and are typically complementary from new physics searches in other channels.Comment: 7 pages, 5 figures, invited talk at PHOTON 2017, draws from 1411.6629, 1609.01762, 1703.10600. v2: references adde