Letters in High Energy Physics

Physical States and Correction Terms of the Supersymmetric c = 1 Model

Omar El Deeb — Sun, 14 Apr 2024 16:49:44 +0000

In this article, we investigate the supersymmetric c = 1 model of superstring theory and demonstrate
how the spectrum of states is expanded and new symmetries of the theory are generated by the existence
of ghost cohomologies. As a result, we establish significant connections between two-dimensional supergravity
and physical theories in higher dimensions. Additionally, we provide a comprehensive guide for
constructing BRST-invariant and nontrivial vertex operators and carry out explicit computations to determine
the correction terms needed to maintain the BRST invariance of the corresponding currents.

Lepton Masses and Mixing in Modular A5 Symmetry

Mohammed Ahmed Abbas — Mon, 29 Apr 2024 08:14:33 +0000

A model based on the modular group A5 is considered to account for lepton masses and mixing. We con-
sider multimoduli scenario, in which charged leptons and neutrinos are assigned to different moduli. Var-
ious models are considered depending on different assignments of modular weights and the mechanis for producing the light neutrino masses.

New Parameterization and Analysis for E6 Inspired 331 Model

Oleg Popov, Rena Ciftci, Abbas Kenan Ciftci — Sun, 05 May 2024 15:20:37 +0000

We present a new parameterization for SU(3)C × SU(3)L × U(1)X extension of the Standard Model, which is inspired by E6 symmetry. The new setup predicts all Cabibbo-Kobayashi-Maskawa mixing angles and quark masses, a total of nine observable variables, within 1–3 standard deviations of the experimental values with a minimum number of input parameters. A detailed numerical analysis and correlations between input parameters and predicted quantities are presented. The best global fit benchmark point corresponds to χ 2 ≈ 0.7 with ∀σ < 0.6. The advantages of the new parameterization and future prospects are discussed as well.

Entanglement Entropy Distributions of a Muon Decay

Shanmuka Shivashankara — Sat, 08 Jun 2024 09:11:56 +0000

Divergences that occur in density matrices of decay and scattering processes are shown to be regularized
by tracing and unitarity or the optical theorem. These divergences are regularized by the lifetime of the decaying particle or the total scattering cross section. Also, these regularizations are shown to give the
expected helicities of final particles. As an illustration, the density matrix is derived for the weak decay of a
polarized muon at rest, µ¯→ νµ(e¯ν¯_e), with Lorentz invariant density matrix entries and unitarity upheld
at tree level. The electron’s von Neumann entanglement entropy distributions are derived with respect
to both the electron’s emission angle and energy. The angular entropy distribution peaks for an electron
emitted backward with respect to the muon’s polarization given a minimum volume regularization larger
than the cube of the muon’s Compton wavelength. The kinematic entropy distribution is maximal at half
the muon’s rest mass energy. These results are similar to the electron’s angular and kinematic decay rate
distributions. Both the density matrix and entanglement entropy can be cast in terms of either ratios of
areas or volumes.

Hot versus Cold Hidden Sectors and Their Effects on Thermal Relics

Pran Nath, Jinzheng Li — Sun, 04 Feb 2024 20:51:42 +0000

A variety of possibilities exist for dark matter aside from WIMPS, such as hidden sector dark matter. We
discuss the synchronous thermal evolution of visible and hidden sectors and show that the density of
thermal relics can change O(100%) and ∆Neff by a factor of up to 105 depending on whether the hidden
sector was hot or cold at the reheat temperature. It is also shown that the approximation of using separate
entropy conservation for the visible and hidden sectors is invalid even for a very feeble coupling between
the two.

Dark Matter and Muon (g − 2) from a Discrete Z4 Symmetric Model

Simran Arora, Bhag Chand Chauhan — Sun, 04 Feb 2024 20:53:08 +0000

The nonzero neutrino mass and nature of Dark Matter (DM) is still unknown within the Standard Model
(SM). In 2021, there was a 4.2σ discrepancy with SM results in the measurement of muon magnetic moment
reported by Fermilab. Recently, Fermilab released its precise results for muon’s magnetic moment, and it
shows a 5.1σ discrepancy. In this work, we study the corelation between neutrino masses, muon (g − 2)
anomaly, and Dark Matter within a framework based on the Z4 extension of the scotogenic model, in which
the neutrino masses are generated at one loop level. We extend the model with a vector-like lepton (VLL)
triplet in order to explain muon (g − 2). Here, the coupling of VLL triplet ψT to inert doublet η provides a
positive contribution to muon anomalous magnetic moment. We also studied the DM phenomenology of
ψT by considering the neutral component of ψT as the lightest DM candidate. We show that, for the mass of
the VLL triplet Mψ in TeV scale, the model can well explain muon (g − 2) anomaly and also gives required
relic density.

New Results on 0νββ Decay from the CUORE Experiment

Alice Campani — Tue, 19 Mar 2024 00:00:00 +0000

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment
searching for neutrinoless double beta decay (0νββ) that has successfully reached the tonne mass scale.
The detector, located at the LNGS in Italy, consists of an array of 988 TeO2 crystals arranged in a compact
cylindrical structure of 19 towers. CUORE began its first physics data run in 2017 at a base temperature of
about 10 mK and has been collecting data continuously since 2019, reaching a TeO2 exposure of 2 tonne-
year in spring 2023. This is the largest amount of data ever acquired with a solid-state cryogenic detector,
which allows for a significant improvement in the sensitivity to 0νββ decay in 130Te. In this article, we
present the analysis of new CUORE data, corresponding to ∼1 tonne · yr TeO2 exposure. This analysis
relies on significant enhancements to the data processing chain and high-level analysis. Combining the new
data with the former data release, we find no evidence for 0νββ decay and set a preliminary 90% credibility
interval Bayesian lower limit of 3.3 · 1025 yr on the 130Te half-life for this process. In the hypothesis that 0νββ
decay is mediated by light Majorana neutrinos, this results in an upper limit on the effective Majorana mass
of 75–255 meV, depending on the nuclear matrix element used.

Search for Leptonic CP Violation with the ESSnuSBplus Project

Tamer Tolba, Jorge Aguilar, Ye Zou — Mon, 25 Mar 2024 12:13:28 +0000

ESSνSB is a design study for a next-generation long-baseline neutrino experiment that aims at the precise
measurement of the CP-violating phase, δCP, in the leptonic sector at the second oscillation maximum. The
conceptual design report published from the first phase of the project showed that after 10 years of data
taking, more than 70% of the possible δCP range will be covered with 5σ C.L. to reject the no-CP-violation
hypothesis. The expected value of δCP precision is smaller than 8◦ for all δCP values. The next phase of the
project, the ESSνSB+, aims at using the intense muon flux produced together with neutrinos to measure
the neutrino-nucleus cross-section, the dominant term of the systematic uncertainty, in the energy range
of 0.2–0.6 GeV, using a Low Energy neutrinos from STORed Muons (LEnuSTORM) and a Low Energy
Monitored Neutrino Beam (LEMNB) facilities.

Charged Higgs Decay to W± and Heavy Neutral Higgs Decaying into τ+τ− in Georgi-Machacek Model at LHC

Swagata Ghosh — Sun, 21 Apr 2024 17:11:24 +0000

The CMS collaboration at the Large Hadron Collider (LHC) searched for a charged Higgs boson, in the mass range of 300 to 700 GeV, decaying into aW± boson and a heavy neutral Higgs boson of mass 200 GeV, which successively decays into a pair of tau leptons, in proton-proton collisions at √ s = 13 TeV. In this letter, focusing on the Georgi-Machacek (GM) model, I discuss the parameter space, allowed by the theoretical and experimental constraints, for which the limits on this process obtained by the CMS can be accommodated.
The study in this letter also shows that, for the choice of the parameters, the decay of the charged Higgs boson H± 3 toW± and a heavy neutral Higgs boson H is preferred over the decay to any gauge boson and any other neutral or charged Higgs bosons. I also present the values of production cross-section times branching ratio for the decay of H to a pair of b-quarks at √s = 14 TeV.

Composite Effective Field Theory Signal from Anomalous Quartic Gauge Couplings for ZZ(→ ℓℓνν)jj and Zγ(→ ννγ)jj Productions

Artur E. Semushin, Evgeny Yu. Soldatov — Tue, 23 Apr 2024 11:13:34 +0000

Parameterization of heavy effects beyond the Standard Model is available using higher-dimension operators
of the effective field theory and their Wilson coefficients, where their values are not known. Experimental
sensitivity to the Wilson coefficients can be significantly changed in case of the usage of composite
anomalous signal, which contains anomalous contributions from background processes in addition to the
conventional ones from the signal process. In this work, this approach is applied to the search for anomalous
quartic gauge couplings with seven EFT operators in the electroweak production of ZZ(→ ℓℓνν)jj and
Zγ(→ ννγ)jj in pp collisions. For the majority of coefficients, sensitivity in the former channel is smaller
than that in the latter one. However, it is shown, that composite anomalous signal affects ZZ(→ ℓℓνν)jj
production stronger than Zγ(→ ννγ)jj production, making sensitivities closer. One-dimensional limits on
theWilson coefficients are changed up to 27.3% and 9.7% due to the background anomalous contributions
in ZZ(→ ℓℓνν)jj and Zγ(→ ννγ)jj productions, respectively.

A New 700GeV Scalar in the LHC Data?

George Rupp, Maurizio Consoli — Tue, 23 Apr 2024 11:19:03 +0000

As an alternative to the metastability of the electroweak vacuum, resulting from perturbative calculations,
one can consider a nonperturbative effective potential which, as at the beginning of the Standard Model,
is restricted to the pure Φ4 sector yet consistent with the known analytical and numerical studies. In this
approach, where the electroweak vacuum is now the lowest-energy state, besides the resonance of mass
mh = 125 GeV defined by the quadratic shape of the potential at its minimum, the Higgs field should
exhibit a second resonance with mass (MH)Theor = 690 (30) GeV associated with the zero-point energy
determining the potential depth. In spite of its large mass, this resonance would couple to longitudinal
Ws with the same typical strength as the low-mass state at 125 GeV and represent a relatively narrow
resonance, mainly produced at LHC by gluon-gluon fusion. In this paper, we review LHC data suggesting
a new resonance of mass (MH)EXP ∼ 682 (10) GeV, with a statistical significance that is far from negligible.

Representation of Fermions in the Pati-Salam Model

Desheng LI, Hong-Fei Zhang — Tue, 23 Apr 2024 11:22:15 +0000

In this paper, a representation of fermions in the Pati-Salam model is suggested. The semileptonic and beyond
standard model flavor changing neutral currents of the Lagrangian in this representation of fermions
are discussed. A pair of possible Cabibbo-Kobayashi-Maskawa and Pontecorvo-Maki-Nakagawa-Sakata
matrices are defined. An effective Lagrangian for this model is given.

A Particle Physics Model without Higgs

Giancarlo Rossi — Tue, 14 May 2024 12:13:39 +0000

In this work, we describe the construction of a particle physics model where chiral symmetry, broken at the
UV scale by “irrelevant” d > 4 operators, is recovered at low energy. In the critical, chiral symmetric theory,
masses of elementary degrees of freedom are generated by a peculiar nonperturbative field-theoretical
mechanism and not as in the Higgs scenario. Consistency of mass formulae with phenomenology requires
the existence of a new sector of superstrongly interacting particles (denoted by Tera-particles), gauge invariantly
coupled to Standard Model matter, living at an energy scale, ΛT, of the order of a few TeVs.
We give the expression of the full Lagrangian of a model encompassing quarks, Tera-quarks and W, as
well as leptons, Tera-leptons, and B gauge bosons when, besides strong, there are Tera-strong and weak
interactions, and also hypercharge is included.We prove that, upon integrating out the (heavy) Tera-DoFs,
the resulting low-energy effective Lagrangian of the critical model essentially coincides with the Standard
Model Lagrangian. This implies that the present model passes all the precision tests that the Standard
Model is able to pass. There are a number of good reasons for considering speculative and unorthodox
theories of this kind. First of all, unlike the Standard Model, in this scenario masses are not free parameters
but are determined by the dynamics of the theory. Secondly, we have a physical understanding of the origin
of the electroweak scale as the scale of a new interaction. Thirdly, we envisage a solution to the strong
CP problem, and last but not least, the Higgs mass tuning problem does not even arise because there is no
fundamental Higgs.