A
bstract
Axion-like particles (ALPs) can provide a portal to new states of a dark sector. We study the phenomenology of this portal when the ALP mainly decays invisibly, while its interaction with ...the standard model sector proceeds essentially via its coupling to electrons and/or photons. We reanalyse existing limits from various collider and beam dump experiments, including in particular ALP production via electron/positron interactions, in addition to the usual production through ALP-photon coupling. We further discuss the interplay between these limits and the intriguing possibility of explaining simultaneously the muon and electron magnetic moment anomalies. Finally, we illustrate the prospects of ALP searches at the LNF positron fixed-target experiment PADME, and the future reach of an upgraded experimental setup.
A
bstract
With an expected rate of about one event per 100,000 top-quark pairs, four top-quark final states very rarely arise at the LHC. Though scarce, they offer a unique window onto top-quark ...compositeness, self-interactions and more generically, onto any top-philic new physics. By employing simplified models featuring heavy resonances, we study the range of validity of effective theory interpretations of current four top-quark analyses at the LHC and establish their future reach at the HL-LHC. We find that for the class of models under consideration, the effective field theory interpretations are not applicable. We therefore present the most up-to-date limits obtained from public CMS analyses using simplified models. Finally, we put forward a novel recasting strategy for the experimental results based on the production of top quarks with large transverse momentum.
A
bstract
Minimal scenarios with light (sub-GeV) dark matter whose relic density is obtained from thermal freeze-out must include new light mediators. In particular, a very well-motivated case is ...that of a new “dark” massive vector gauge boson mediator. The mass term for such mediator is most naturally obtained by a “dark Higgs mechanism” which leads to the presence of an often long-lived dark Higgs boson whose mass scale is the same as that of the mediator. We study the phenomenology and experimental constraints on two minimal, self-consistent dark sectors that include such a light dark Higgs boson. In one the dark matter is a pseudo-Dirac fermion, in the other a complex scalar. We find that the constraints from BBN and CMB are considerably relaxed in the framework of such minimal dark sectors. We present detection prospects for the dark Higgs boson in existing and projected proton beam-dump experiments. We show that future searches at experiments like Xenon1T or LDMX can probe all the relevant parameter space, complementing the various upcoming indirect constraints from astrophysical observations.
A
bstract
Pairs of Standard Model fermions form dimension-3 singlet operators that can couple to new dark sector states. This “fermion portal” is to be contrasted with the lower-dimensional Higgs, ...vector and neutrino singlet portals. We characterise its distinct phenomenology and place effective field theory bounds on this framework, focusing on the case of fermion portals to a pair of light dark sector fermions. We obtain current and projected limits on the dimension-6 effective operator scale from a variety of meson decay experiments, missing energy and long-lived particle searches at colliders, as well as astrophysical and cosmological bounds. The DarkEFT public code is made available for recasting these limits, which we illustrate with various examples including an integrated- out heavy dark photon.
The existence of colour-octet scalar states, often dubbed sgluons, is predicted in many extensions of the Standard Model of particle physics, such as supersymmetric realisations featuring Dirac ...gauginos. Such states have a large pair-production rate at hadron colliders and mainly decay into pairs of jets and top quarks. Consequently, they represent a primary target for experimental searches for new resonances in the multijet and multitop channels at the Large Hadron Collider. Adopting a phenomenologically-motivated simplified model, we reinterpret the results of a recent experimental search for the four-top-quark Standard Model signal, from which we constrain the sgluon mass to be larger than about 1.06 TeV. We additionally consider how modifications of the existing four-top-quark studies could enhance our ability to unravel the presence of scalar octets in data.
Gauge SU(2)f flavour transfers Darmé, Luc; Deandrea, Aldo; Mahmoudi, Farvah
The journal of high energy physics,
05/2024, Letnik:
2024, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
We introduce the idea of flavour transfer from a non-abelian horizontal SU(2)
f
flavour gauge group embedded in the Standard Model flavour structure. The new flavour vector bosons, in the ...mass range from the tens of GeV to multi-TeV, do not induce large flavour-changing neutral currents and meson oscillations, which usually provide the dominant constraints on this type of structure. Instead, the main constraints arise from “flavour-transfer” operators that we will study in detail. Several explicit models are presented and their prospects are thoroughly explored, including their phenomenology in the lepton and quark sectors at colliders and lower energy experiments. We perform a complete numerical fit in one such scenario, showing that LHC-based lepton-flavour violating searches are competitive with intensity frontier observables.
We study a class of gauge groups that can automatically yield a perturbatively exact Peccei-Quinn symmetry, and we outline a model in which the axion quality problem is solved at all operator ...dimensions. Gauge groups belonging to this class can also enforce and protect accidental symmetries of the clockwork type, and we present a toy model where an "invisible" axion arises from a single low scale breaking of the gauge and global symmetries.
A
bstract
Motivated by the recent anomalies in
b
→
s
transitions that emerged at LHCb, we consider a model with an
L
μ
−
L
τ
gauge symmetry and additional vector-like fermions. We find that by ...introducing supersymmetry the model can be made consistent with the long-standing deviation in the measured value of the anomalous magnetic moment of the muon, (
g
− 2)
μ
, and neutralino dark matter of broad mass ranges and properties. In particular, dark matter candidates include the well-known 1 TeV higgsino, which in the MSSM is typically not compatible with solutions to the (
g
− 2)
μ
puzzle. Moreover, its spin-independent cross section could be at the origin of the recent small excess in XENON-1T data. We apply to the model constraints arising from flavor precision measurements and direct searches at the Large Hadron Collider and show that they do not currently exclude the relevant parameter space regions.
The axion flavour connection Darmé, Luc; Nardi, Enrico; Smarra, Clemente
The journal of high energy physics,
02/2023, Letnik:
2023, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A
bstract
A local flavour symmetry acting on the quarks of the Standard Model can automatically give rise to an accidental global U(1) which remains preserved from sources of explicit breaking up to ...a large operator dimension, while it gets spontaneously broken together with the flavour symmetry. Such non-fundamental symmetries are often endowed with a mixed QCD anomaly, so that the strong CP problem is automatically solved via the axion mechanism. We illustrate the general features required to realise this scenario, and we discuss a simple construction based on the flavour group SU(3)
×
SU(2)
×
U(1)
F
to illustrate how mass hierarchies can arise while ensuring at the same time a high quality Peccei-Quinn symmetry.
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