Search for electroweak production of charginos and sleptons decaying into final states with two leptons and missing transverse momentum in $$\sqrt{s}=13$$ $$\text {TeV}$$ pp collisions using the ATLAS detector

We investigate solutions to the flavour anomalies in B decays based on loop diagrams of a "split" dark sector characterised by the simultaneous presence of heavy particles at the TeV scale and light particles around and below the B-meson mass scale. We show that viable parameter space exists for solutions based on penguin diagrams with a vector mediator, while minimal constructions relying on box diagrams are in strong tension with the constraints from the LHC, LEP, and the anomalous magnetic moment of the muon. In particular, we highlight a regime where the mediator lies close to the B-meson mass, naturally realising a resonance structure and a q 2-dependent effective coupling. We perform a full fit to the relevant flavour observables and analyse the constraints from intensity frontier experiments. Besides new measurements of the anomalous magnetic moment of the muon, we find that decays of the B meson, B s-mixing, missing energy searches at Belle-II, and LHC searches for top/bottom partners can robustly test these scenarios in the near future.

Section: Jhep08(2020)148mentioning

confidence: 99%

Flavour anomalies from a split dark sector

Fedele

Kowalska

Sessolo

2020

“…8 At the LHC there is currently no specific search for particles with the quantum numbers of S and X. However, slepton pair production with their subsequent decays to a lepton plus a neutralino provide the same signal and thus, we can make a reinterpretation of the corresponding searches at CMS [57] and ATLAS [58]. The CMS slepton search [57] is based on 35.9/fb, while ATLAS' chargino and slepton search [58] uses 139/fb.…”

Section: Resultsmentioning

confidence: 99%

Minimal 3-loop neutrino mass models and charged lepton flavor violation

Cepedello

Hirsch

Rocha-Morán³

et al. 2020

We study charged lepton flavor violation for the three most popular 3-loop Majorana neutrino mass models. We call these models "minimal" since their particle content correspond to the minimal sets for which genuine 3-loop models can be constructed. In all the three minimal models the neutrino mass matrix is proportional to some powers of Standard Model lepton masses, providing additional suppression factors on top of the expected loop suppression. To correctly explain neutrino masses, therefore large Yukawa couplings are needed in these models. We calculate charged lepton flavor violating observables and find that the three minimal models survive the current constraints only in very narrow regions of their parameter spaces.

“…In the following we are focusing on the simplest topology pp → L + L − → µ + µ − + / E T . The latest available analysis of this signal has been presented by ATLAS in [70] (see also the results with a smaller data set in [71]). The resulting bound on the production cross section can be as strong as σ 0.2 fb (for M L M S 1 ), which corresponds to M L 900 GeV (according to the LO production cross section as calculated by MadGraph5 [67]).…”

Section: Lhc Phenomenologymentioning

confidence: 99%

“…The most sensitive signature is thus again 2 [70] or 3 [72] leptons (from the leptonic decays of the gauge bosons) and / E T . This searches can constrain Higgsino-like charginos and neutralinos with masses up to about 600 GeV.…”

Section: Jhep10(2020)070mentioning

confidence: 99%

“…The hatched cyan area corresponds to the region excluded by the ATLAS search [71] as recast in [15]. The dashed cyan line shows how the bound increases due to the updated analysis in [70]: this limit is an estimate based on the excluded production cross section as reported in the auxiliary material of the ATLAS article. As we mentioned in section 4.1, we expect that this search can exclude our vectorlike JHEP10(2020)070…”

Section: Jhep10(2020)070mentioning

confidence: 99%

See 1 more Smart Citation

Simple model for large CP violation in charm decays, B-physics anomalies, muon g − 2 and dark matter

Liu

Zhu

2020

We present a minimal extension of the Standard Model that can simultaneously account for the anomalies in semi-leptonic B meson decays and the muon g − 2, give large CP violation in charm decays (up to the value recently measured by LHCb), and provide thermal-relic dark matter, while evading all constraints set by other flavour observables, LHC searches, and dark matter experiments. This is achieved by introducing only four new fields: a vectorlike quark, a vectorlike lepton, and two scalar fields (a singlet and a doublet) that mix due to the electroweak symmetry breaking and provide the dark matter candidate. The singlet-doublet mixing induces chirally-enhanced dipole transitions, which are crucial for the explanation of the muon g − 2 discrepancy and the large charm CP violation, and allows to achieve the observed dark matter density in wide regions of the parameter space.