Physics beyond colliders at CERN: beyond the Standard Model working group report

Beacham, J. B.; Burrage, Clare; Curtin, David; Roeck, A. De; Evans, Justin J.; Feng, Jonathan L.; Gatto, C.; Gninenko, S.; Hartin, A.; Irastorza, I.G.; Jaeckel, Joerg; Jungmann, K.; Kirch, K.; Kling, Felix; Knapen, Simon; Lamont, Mike; Lanfranchi, G.; Lazzeroni, C.; Lindner, A.; Martínez-Vidal, F.; Moulson, M.; Neri, N.; Papucci, Michele; Morales, M. I. Pedraza; Petridis, K.; Pospelov, Maxim; Rozanov, A.; Ruoso, G.; Schuster, Philip; Semertzidis, Yannis K.; Spadaro, T.; Vallée, Claude; Wilkinson, G.

doi:10.1088/1361-6471/ab4cd2

Cited by 487 publications

(656 citation statements)

References 358 publications

(706 reference statements)

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“…In the present study, we will restrict ourselves to HNL masses between the K and D s thresholds. Masses below the K threshold have already been heavily constrained [11], while above the D s mass, HNLs are mainly produced in B meson decays, whose spectrum cannot be directly measured at the beam dump, making our analysis more sensitive to modeling errors.…”

Section: Hnl Production and Decay At Shipmentioning

confidence: 99%

“…The results are presented in fig. 9, along with various existing exclusion bounds and detection sensitivity 9 limits for planned or proposed experiments, extracted from the report of the Physics Beyond Colliders working group [11]. We only show the sensitivities of experiments which can not only set exclusion bounds, but also reconstruct the HNL mass, should it be observed.…”

Section: Sensitivity To Lepton Number Violationmentioning

confidence: 99%

“…In practice, we choose a mass range spanning the region between the K and D s thresholds, and consider several benchmark models with fixed |Θ e | 2 : |Θ µ | 2 ratios. 11 For each choice of physical parameters, we sample 3·10 6 events with uniform weights. This is done by sampling sufficiently many weighted events and, as they are being generated, "unweighting" them by performing rejection sampling with an acceptance probability proportional to their weight.…”

Section: B1 Datasetmentioning

confidence: 99%

“…From the FIP (feebly interacting particles) search point of view [11], HNLs with masses below that of a B meson are the most accessible in the foreseeable future. There is a vast program to search for HNLs at intensity frontier experiments, either LHC-based, such as MATHUSLA [12,13], FASER [14], CODEX-b [15] and AL3X [16], or at beam-dump facilities, such as NA62 ++ [17] and SHiP [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

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Dirac vs. Majorana HNLs (and their oscillations) at SHiP

Tastet

Timiryasov

2020

J. High Energ. Phys.

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SHiP is a proposed high-intensity beam dump experiment set to operate at the CERN SPS. It is expected to have an unprecedented sensitivity to a variety of models containing feebly interacting particles, such as Heavy Neutral Leptons (HNLs). Two HNLs or more could successfully explain the observed neutrino masses through the seesaw mechanism. If, in addition, they are quasi-degenerate, they could be responsible for the baryon asymmetry of the Universe. Depending on their mass splitting, HNLs can have very different phenomenologies: they can behave as Majorana fermions-with lepton number violating (LNV) signatures, such as same-sign dilepton decays-or as Dirac fermions with only lepton number conserving (LNC) signatures. In this work, we quantitatively demonstrate that LNV processes can be distinguished from LNC ones at SHiP, using only the angular distribution of the HNL decay products. Accounting for spin correlations in the simulation and using boosted decision trees for discrimination, we show that SHiP will be able to distinguish Majorana-like and Dirac-like HNLs in a significant fraction of the currently unconstrained parameter space. If the mass splitting is of order 10 −6 eV, SHiP could even be capable of resolving HNL oscillations, thus providing a direct measurement of the mass splitting. This analysis highlights the potential of SHiP to not only search for feebly interacting particles, but also perform model selection.

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Section: Hnl Production and Decay At Shipmentioning

confidence: 99%

Section: Sensitivity To Lepton Number Violationmentioning

confidence: 99%

Section: B1 Datasetmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dirac vs. Majorana HNLs (and their oscillations) at SHiP

Tastet

Timiryasov

2020

J. High Energ. Phys.

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“…See the scalar-portal discussion in Ref. [41] for a summary of the update-to-date experimental constraints for m hs < ∼ 10 GeV.…”

Section: A the Light Sub-gev Scalar Boson Casementioning

confidence: 99%

Probing long-lived particles at Higgs factories

Cheung

Wang

2020

Phys. Rev. D

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We study displaced vertex signatures of long-lived particles (LLPs) from exotic Higgs decays in the context of a Higgs-portal model and a neutral-naturalness model at the CEPC and FCCee. Such two models feature two representative mass ranges for LLPs, which show very different behavior in their decay signatures. The Higgs-portal model contains a very light sub-GeV scalar boson stemming from a singlet scalar field appended to the Standard Model. Such a light scalar LLP decays into a pair of muons or pions, giving rise to a distinctive signature of collimated muonjet or pion-jet, thanks to the sub-GeV mass. On the other hand, the neutral-naturalness model, e.g., folded supersymmetry, predicts the lightest mirror glueball of mass O(10) GeV, giving rise to long decays with a large transverse impact parameter because of the relatively large mass. Utilizing such distinct characteristics to remove the background, we estimate the sensitivities of searches for light scalar bosons and mirror glueballs at the CEPC and FCC-ee. We find either complementary or stronger coverage compared to the previous results in the similar contexts.

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Fast Apparent Oscillations of Fundamental Constants

et al. 2020

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Precision spectroscopy of atoms and molecules allows one to search for and to put stringent limits on the variation of fundamental constants. These experiments are typically interpreted in terms of variations of the fine structure constant and the electron-to-proton mass ratio = m e ∕m p . Atomic spectroscopy is usually less sensitive to other fundamental constants, unless the hyperfine structure of atomic levels is studied. However, the number of possible dimensionless constants increases when allowed for fast variations of the constants, where "fast" is determined by the time scale of the response of the studied species or experimental apparatus used. In this case, the relevant dimensionless quantity is, for example, the ratio m e ∕⟨m e ⟩ and ⟨m e ⟩ is the time average. In this sense, one may say that the experimental signal depends on the variation of dimensionful constants (m e in this example).

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Physics beyond colliders at CERN: beyond the Standard Model working group report

Cited by 487 publications

References 358 publications

Dirac vs. Majorana HNLs (and their oscillations) at SHiP

Dirac vs. Majorana HNLs (and their oscillations) at SHiP

Probing long-lived particles at Higgs factories

Fast Apparent Oscillations of Fundamental Constants

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