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A bstract Thermal light dark matter (LDM) with particle masses in the 1 MeV–1 GeV range could successfully explain the observed dark matter abundance as a relic from the primordial Universe. In this picture, a new feeble interaction acts as a “portal” between the Standard Model and LDM particles, allowing for the exploration of this paradigm at accelerator experiments. In the last years, the “missing energy” experiment NA64 e at CERN SPS (Super Proton Synchrotron) has set world-leading constraints in the vector-mediated LDM parameter space, by exploiting a 100 GeV electron beam impinging on an electromagnetic calorimeter, acting as an active target. In this paper, we report a detailed description of the analysis of a preliminary measurement with a 70 GeV/c positron beam at NA64 e , performed during summer 2023 with an accumulated statistics of 1 . 596 × 10 10 positrons on target (hereafter referred to as e + OT). This data set was analyzed with the primary aim of evaluating the performance of the NA64 e detector with a lower energy positron beam, towards the realization of the post-LS3 program. The analysis results, other than additionally probing unexplored regions in the LDM parameter space, provide valuable information towards the future NA64 e positron campaign.

Light scalars that couple to leptons are common figures in beyond the Standard Model endeavors. Considering a scalar that has universal and couplings to leptons only, we compute this leptophilic scalar contribution to the e - e + → τ + τ - S production cross section with S → e + e - ( μ + μ - ) . We later compare the expected signal with recent data from the BELLE collaboration collected near the resonance Υ ( 4 S ) with L = 626 f b - 1 of integrated luminosity to place limits on the couplings-mass plane for the 4 MeV-6.5 GeV mass range. We then extended this analysis to a more general one e - e + → ℓ + ℓ - S production cross section where ℓ = e , μ , τ with S → e + e - ( μ + μ - ) , showing that BELLE constitutes an excellent laboratory for light scalars, where can be derived constraints stronger than those derived stemming from the g-2 of the electron or muon.

We derive the discovery potential of a leptophilic Z ′ , and a Z ′ rising from a S U ( 3 ) C × S U ( 3 ) L × U ( 1 ) N symmetry at the Compact Linear Collider (CLIC), which is planned to host e + e - collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a 5 σ signal of a 1 - 5  TeV leptophilic Z ′ with less than 1 fb - 1 of integrated luminosity in the most favorable cases. As for the Z ′ belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to impose M Z ′ > 3  TeV with L = 2 fb - 1 .

We derive the discovery potential of a leptophilic [Formula omitted], and a [Formula omitted] rising from a [Formula omitted] symmetry at the Compact Linear Collider (CLIC), which is planned to host [Formula omitted] collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a [Formula omitted] signal of a [Formula omitted] TeV leptophilic [Formula omitted] with less than 1 fb [Formula omitted] of integrated luminosity in the most favorable cases. As for the [Formula omitted] belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to impose [Formula omitted] TeV with [Formula omitted] fb [Formula omitted].

We derive the discovery potential of a leptophilic$$Z^\\prime $$Z ′ , and a$$Z^\\prime $$Z ′ rising from a$$SU(3)_C \\times SU(3)_L \\times U(1)_N$$S U ( 3 ) C × S U ( 3 ) L × U ( 1 ) N symmetry at the Compact Linear Collider (CLIC), which is planned to host$$e^+e^-$$e + e - collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a$$5\\sigma $$5 σ signal of a$$1-5$$1 - 5  TeV leptophilic$$Z^\\prime $$Z ′ with less than 1 fb$$^{-1}$$- 1 of integrated luminosity in the most favorable cases. As for the$$Z^\\prime $$Z ′ belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to impose$$M_{Z^\\prime } > 3$$M Z ′ > 3  TeV with$${\\mathcal {L}}=2$$L = 2 fb$$^{-1}$$- 1 .

Abstract Light scalars that couple to leptons are common figures in beyond the Standard Model endeavors. Considering a scalar that has universal and couplings to leptons only, we compute this leptophilic scalar contribution to thee⁻e⁺ → τ ⁺τ ⁻ S e - e + → τ + τ - S production cross section withS → e⁺e⁻(μ ⁺μ ⁻)S → e + e - ( μ + μ - ) . We later compare the expected signal with recent data from the BELLE collaboration collected near the resonanceΥ (4S)Υ ( 4 S ) with\\mathscr L=626 fb⁻¹L = 626 f b - 1 of integrated luminosity to place limits on the couplings-mass plane for the 4 MeV-6.5 GeV mass range. We then extended this analysis to a more general onee⁻e⁺ → ℓ ⁺ℓ ⁻ Se - e + → ℓ + ℓ - S production cross section whereℓ =e,μ ,τ ℓ = e , μ , τ withS → e⁺e⁻(μ ⁺μ ⁻)S → e + e - ( μ + μ - ) , showing that BELLE constitutes an excellent laboratory for light scalars, where can be derived constraints stronger than those derived stemming from the g-2 of the electron or muon.

A bstract The inclusion of an additional U(1) gauge L μ − L τ symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm assumes the existence of a new, light Z ′ vector boson, with dominant coupling to μ and τ leptons and interacting with electrons via a loop mechanism. The L μ − L τ model can also explain the Dark Matter relic abundance, by assuming that the Z ′ boson acts as a “portal” to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the Z ′ search performed by the NA64- e experiment at CERN SPS, that collected ~ 9 × 10 11 100 GeV electrons impinging on an active thick target. Despite the suppressed Z ′ production yield with an electron beam, NA64- e provides the first accelerator-based results excluding the g − 2 preferred band of the Z ′ parameter space in the 1 keV < m Z ′ ≲ 2 MeV range, in complementarity with the limits recently obtained by the NA64- μ experiment with a muon beam.

A model-agnostic search for Beyond the Standard Model physics is presented, targeting final states with at least four light leptons (electrons or muons). The search regions are separated by event topology and unsupervised machine learning is used to identify anomalous events in the full 140 fb - 1 of proton–proton collision data collected with the ATLAS detector during Run 2. No significant excess above the Standard Model background expectation is observed. Model-agnostic limits are presented in each topology, along with limits on several benchmark models including vector-like leptons, wino-like charginos and neutralinos, or smuons. Limits are set on the flavourful vector-like lepton model for the first time.

Higgs boson production cross-sections via gluon–gluon fusion and vector-boson fusion in proton–proton collisions are measured in the H → W W ∗ → ℓ ν ℓ ν decay channel. The Large Hadron Collider delivered proton–proton collisions at a centre-of-mass energy of 13 TeV between 2015 and 2018, which were recorded by the ATLAS detector, corresponding to an integrated luminosity of 140 fb - 1 . The total cross-sections for Higgs boson production by gluon–gluon fusion and vector-boson fusion times the H → W W ∗ branching ratio are measured to be 12 . 4 - 1.2 + 1.3 pb and 0 . 79 - 0.16 + 0.18 pb , respectively, in agreement with the Standard Model predictions. Higgs boson production is further characterised through measurements of Simplified Template Cross-Sections in a total of fifteen kinematic fiducial regions. A new scheme of kinematic fiducial regions has been introduced to enhance the sensitivity to CP-violating effects in Higgs boson interactions. Both schemes are used to constrain CP-even and CP-odd dimension-six operators in the Standard Model effective field theory

Abstract We derive the discovery potential of a leptophilicZ^(′) Z ′ , and aZ^(′) Z ′ rising from aSU(3)_(C) × SU(3)_(L) × U(1)_(N)S U ( 3 ) C × S U ( 3 ) L × U ( 1 ) N symmetry at the Compact Linear Collider (CLIC), which is planned to hoste⁺e⁻e + e - collisions with 3 TeV center-of-mass energy. We perform an optimized selection cut strategy on the transverse momentum, pseudorapidity, and invariant mass of the dileptons in order to enhance the collider sensitivity. We find that CLIC can potentially reach a5σ 5 σ signal of a1-51 - 5  TeV leptophilicZ^(′) Z ′ with less than 1 fb⁻¹- 1 of integrated luminosity in the most favorable cases. As for theZ^(′) Z ′ belonging to a 3-3-1 symmetry, CLIC will offer a complementary probe with the potential to imposeM_(Z^(′)) > 3M Z ′ > 3  TeV with𝓛=2L = 2 fb⁻¹- 1 .