Search for neutrinoless double beta decay of ¹¹⁶Cd and ⁸²Se and calorimeter simulations for the SuperNEMO experiment

textUsing the NEMO-3 detector, 410.4 g of ¹¹⁶Cd with a total exposure of 1.65 kg• y and 932 g of ⁸²Se with a total exposure of 3.75 kg• y were used to measure the half-life of two-neutrino double beta decay (2[nu][beta][beta]) to the ground states of ¹¹⁶Sn and ⁸²Kr and to place a lower limit on the neutrinoless double becay decay (0[nu][beta][beta]) to the same ground states. Under the single-states dominance hypothesis, the 2[nu][beta][beta] half-lives are found to be T 1/2(¹¹⁶Cd) = (2.90 ± 0.03(stat) ± 0.15(syst)×10¹⁹ yr and T 1/2(⁸²Se) = [10.62±0.11(stat)±0.56(syst)]×10¹⁹ yr. 0[nu][beta][beta] is excluded to 90% confidence level at T 1/2 ≥ 1.12 × 10²³ yr for ¹¹⁶Cd and T 1/2 ≥ 3.90 × 10²³ yr for ⁸²Se. These half-lives correspond to effective Majorana neutrino masses of m ≤ (4.33 - 5.54) eV and m ≤ (2.28 - 2.82) eV, respectively, in the light Majorana exchange mechanism.Physic

Measurements of Beam Backgrounds in SuperKEKB Phase 2

The high design luminosity of the SuperKEKB electron-positron collider will result in challenging levels of beam-induced backgro unds in the interaction region. Understanding and mitigating these backgrounds is critical to the success of the Belle~II experi ment. We report on the first background measurements performed after roll-in of the Belle II detector, a period known as SuperKE KB Phase 2, utilizing both the BEAST II system of dedicated background detectors and the Belle II detector itself. We also repor t on first revisions to the background simulation made in response to our findings. Backgrounds measured include contributions f rom synchrotron radiation, beam-gas, Touschek, and injection backgrounds. At the end of Phase 2, single-beam backgrounds origina ting from the 4 GeV positron Low Energy Ring (LER) agree reasonably well with simulation, while backgrounds from the 7 GeV elect ron High Energy Ring (HER) are approximately one order of magnitude higher than simulation. We extrapolate these backgrounds for ward and conclude it is safe to install the Belle II vertex detector

Measurement of the Ωc0\Omega_c^0 lifetime at Belle II

We report on a measurement of the $\Omega_c^0$ lifetime using $\Omega_c^0 \to \Omega^-\pi^+$ decays reconstructed in $e^+e^-\to c\bar{c}$ data collected by the Belle II experiment and corresponding to $207~{\rm fb^{-1}}$ of integrated luminosity. The result, $\rm\tau(\Omega_c^0)=243\pm48( stat)\pm11(syst)~fs$, agrees with recent measurements indicating that the $\Omega_c^0$ is not the shortest-lived weakly decaying charmed baryon

Measurement of the Ωc0\Omega_c^0 lifetime at Belle II

We report on a measurement of the $\Omega_c^0$ lifetime using $\Omega_c^0 \to \Omega^-\pi^+$ decays reconstructed in $e^+e^-\to c\bar{c}$ data collected by the Belle II experiment and corresponding to $207~{\rm fb^{-1}}$ of integrated luminosity. The result, $\rm\tau(\Omega_c^0)=243\pm48( stat)\pm11(syst)~fs$, agrees with recent measurements indicating that the $\Omega_c^0$ is not the shortest-lived weakly decaying charmed baryon

Measurement of the Ωc0\Omega_c^0 lifetime at Belle II

We report on a measurement of the $\Omega_c^0$ lifetime using $\Omega_c^0 \to \Omega^-\pi^+$ decays reconstructed in $e^+e^-\to c\bar{c}$ data collected by the Belle II experiment and corresponding to $207~{\rm fb^{-1}}$ of integrated luminosity. The result, $\rm\tau(\Omega_c^0)=243\pm48( stat)\pm11(syst)~fs$, agrees with recent measurements indicating that the $\Omega_c^0$ is not the shortest-lived weakly decaying charmed baryon

The International Linear Collider: Report to Snowmass 2021

International audienceThe International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community

Test of light-lepton universality in τ\tau decays with the Belle II experiment

International audienceWe present a measurement of the ratio $R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau)$ of branching fractions $\mathcal{B}$ of the $\tau$ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB $e^+e^-$ collider. The sample has an integrated luminosity of 362 fb$^{-1}$ at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, $R_\mu = 0.9675 \pm 0.0007 \pm 0.0036$, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the $W$ boson in $\tau$ decays of $0.9974 \pm 0.0019$, in agreement with the standard model expectation of unity

The International Linear Collider: Report to Snowmass 2021

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community