Phenomenology of General Gauge Mediation in light of a 125 GeV Higgs

We explore the phenomenology of the full General Gauge Mediation parameter space in the MSSM focusing on the consequences of having a fundamental Higgs around 125 GeV. Assuming GUT-complete structure of the hidden sector, we allow for deviations from the strict definition of gauge mediated SUSY-breaking coming from mild violations of messenger-parity and from extra couplings between the Higgs multiplets and the hidden sector. Relaxing the GUT assumption, our parameter space is defined by the property of having vanishing A-terms at the messenger scale. In this extended setup we focus on the possibility of splitting the SU(3) mass parameters of GGM. In all these scenarios we investigate the possible spectra, discussing to what extent having an Higgs mass around 125 GeV is constraining the GGM parameter space and what are the possible signatures at LHC.Comment: 83 pages, 29 figures; v2: minor corrections, references adde

Di-photon excess illuminates Dark Matter

We propose a simplified model of dark matter with a scalar mediator to accommodate the di-photon excess recently observed by the ATLAS and CMS collaborations. Decays of the resonance into dark matter can easily account for a relatively large width of the scalar resonance, while the magnitude of the total width combined with the constraint on dark matter relic density lead to sharp predictions on the parameters of the Dark Sector. Under the assumption of a rather large width, the model predicts a signal consistent with ~300 GeV dark matter particle in channels with large missing energy. This prediction is not yet severely bounded by LHC Run I searches and will be accessible at the LHC Run II in the jet plus missing energy channel with more luminosity. Our analysis also considers astrophysical constraints, pointing out that future direct detection experiments will be sensitive to this scenario.Comment: 23 pages, 8 figures. Added 2 figures and more discussion

New LHC bound on low-mass diphoton resonances

We derive a new bound on diphoton resonances using inclusive diphoton cross section measurements at the LHC, in the so-far poorly constrained mass range between the Upsilon and the SM Higgs. This bound sets the current best limit on axion-like particles that couple to gluons and photons, for masses between 10 and 65 GeV. We also estimate indicative sensitivities of a dedicated diphoton LHC search in the same mass region, at 7, 8 and 14 TeV. As a byproduct of our analysis, we comment on the axion-like particle interpretation of the CMS excesses in low-mass dijet and diphoton searches.Comment: 7 pages + appendices, 5 figures, 2 tables. v2: discussion improved, new bound derived also from Tevatron, conclusions unchanged. v3: matches PLB versio

The Axiflavon

We show that solving the flavor problem of the Standard Model with a simple $U(1)_H$ flavor symmetry naturally leads to an axion that solves the strong CP problem and constitutes a viable Dark Matter candidate. In this framework, the ratio of the axion mass and its coupling to photons is related to the SM fermion masses and predicted within a small range, as a direct result of the observed hierarchies in quark and charged lepton masses. The same hierarchies determine the axion couplings to fermions, making the framework very predictive and experimentally testable by future axion and precision flavor experiments.Comment: 6 pages, typos corrected, references adde

On Lorentz-Violating Supersymmetric Quantum Field Theories

We study the possibility of constructing Lorentz-violating supersymmetric quantum field theories under the assumption that these theories have to be described by lagrangians which are renormalizable by weighted power counting. Our investigation starts from the observation that at high energies Lorentz-violation and the usual supersymmetry algebra are algebraically compatible. Demanding linearity of the supercharges we see that the requirement of renormalizability drastically restricts the set of possible Lorentz-violating supersymmetric theories. In particular, in the case of supersymmetric gauge theories the weighted power counting has to coincide with the usual one and the only Lorentz-violating operators are introduced by some weighted constant c that explicitly appears in the supersymmetry algebra. This parameter does not renormalize and has to be very close to the speed of light at low energies in order to satisfy the strict experimental bounds on Lorentz violation. The only possible models with non trivial Lorentz-violating operators involve neutral chiral superfields and do not have a gauge invariant extension. We conclude that, under the assumption that high-energy physics can be described by a renormalizable Lorentz-violating extensions of the Standard Model, the Lorentz fine tuning problem does not seem solvable by the requirement of supersymmetry.Comment: 22 pages, 2 figure

The Supercooling Window at Weak and Strong Coupling

Supercooled first order phase transitions are typical of theories where conformal symmetry is predominantly spontaneously broken. In these theories the fate of the flat scalar direction is highly sensitive to the size and the scaling dimension of the explicit breaking deformations. For a given deformation, the coupling must lie in a particular region to realize a supercooled first order phase transition. We identify the supercooling window in weakly coupled theories and derive a fully analytical understanding of its boundaries. Mapping these boundaries allows us to identify the deformations enlarging the supercooling window and to characterize their dynamics analytically. For completeness we also discuss strongly coupled conformal field theories with an holographic dual, where the complete characterization of the supercooling window is challenged by calculability issues.Comment: 16 pages + appendices, 12 figures; v2: minor typo correcte

Probing naturally light singlets with a displaced vertex trigger

We investigate the physics case for a dedicated trigger on a low mass, hadronic displaced vertex at the high luminosity LHC, relying on the CMS phase II track trigger. We estimate the trigger efficiency with a simplified simulation of the CMS track trigger and show that the L1 trigger rate from fake vertices, B meson decays and secondary interactions with the detector material can likely be brought down to the kHz level with a minimal set of cuts. While it would with any doubt be a severe experimental challenge to implement, we conclude that a displaced vertex trigger could open qualitatively new parameter space for exotic Higgs decays, exotic B decays and even direct production of light resonances. We parametrize the physics potential in terms of a singlet scalar mixing with the Standard Model Higgs and an axion-like particle with a coupling to gluons, and review a number or relevant models motivated by the hierarchy and strong CP problems, dark matter and baryogenesis.Comment: 18 pages, 8 figure

Anatomy of new SUSY breaking holographic RG flows

We find and thoroughly study new supergravity domain wall solutions which are holographic realizations of supersymmetry breaking strongly coupled gauge theories. We set ourselves in an N=2 gauged supergravity with a minimal content in order to reproduce a dual N=1 effective SCFT which has a U(1)_R symmetry, a chiral operator whose components are responsible for triggering the RG flow, and an additional U(1)_F symmetry. We present a full three dimensional parameter space of solutions, which generically break supersymmetry. Some known solutions are recovered for specific sets of values of the parameters, with the new solutions interpolating between them. The generic backgrounds being singular, we provide a stability test of their dual theories by showing that there are no tachyonic resonances in the two point correlators. We compute the latter by holographic renormalization. We also carefully analyze the appearance of massless modes, such as the dilaton and the R axion, when the respective symmetries are spontaneously broken, and their lifting when the breaking is explicit. We further comment on the application of such class of backgrounds as archetypes of strongly coupled hidden sectors for gauge mediation of supersymmetry breaking. In particular, we show that it is possible to model in this way all types of hierarchies between the visible sector gaugino and sfermion masses.Comment: 70 pages, 20 figure

Looking forward to Lepton-flavor-violating ALPs

We assess the status of past and future experiments on lepton flavor violating (LFV) muon and tau decays into a light, invisible, axion-like particle (ALP), $a$. We propose a new experimental setup for MEG II, the MEGII-fwd, with a forward calorimeter placed downstream from the muon stopping target. Searching for $\mu \to e a$ decays MEGII-fwd is maximally sensitive to LFV ALPs, if these have nonzero couplings to right-handed leptons. The experimental set-up suppresses the (left-handed) Standard Model background in the forward direction by controlling the polarization purity of the muon beam. The reach of MEGII-fwd is compared with the present constraints, the reach of Mu3e and the Belle-II reach from $\tau \to \ell a$ decays. We show that a dedicated experimental campaign for LFV muon decays into ALPs at MEG II and Mu3e will be able to probe the ALP parameter space in an unexplored region well beyond the existing astrophysical constraints. We study the implications of these searches for representative LFV ALP models, where the presence of a light ALP is motivated by neutrino masses, the strong CP problem and/or the SM flavor puzzle. To this extent we discuss the majoron in low-scale seesaw setups and introduce the LFV QCD axion, the LFV axiflavon and the leptonic familon, paying particular attention to the cases where the LFV ALPs constitute cold dark matter.Comment: 62 pages, 13 figures, 4 tables, minor changes, matching published versio

Fusing Vectors into Scalars at High Energy Lepton Colliders

We study vector boson fusion production of new scalar singlets at high energy lepton colliders. We find that CLIC has the potential to test single production cross-sections of a few tens of attobarns in di-Higgs and di-boson final states. In models with a sizeable singlet-Higgs mixing, these values correspond to a precision in Higgs couplings of order 0.1% or better. We compare our sensitivities with those of the LHC and interpret our results in well-motivated models like the Twin Higgs, the NMSSM and axion-like particles. Looking forward to even higher energy machines, we show that the reach of muon colliders like LEMMA or MAP overcomes the one of future hadron machines like FCC-hh. We finally study the pair production of the new scalar singlets via an off-shell Higgs. This process does not vanish for small mixings and will constitute a crucial probe of models generating a first order electro-weak phase transition.Comment: 34 pages, 16 figures, 2 tables. v2: discussion improved, figures and references added, typos and numerical glitches fixed, conclusions unchange