TESS Reveals a Short-period Sub-Neptune Sibling (HD 86226c) to a Known Long-period Giant Planet

The Transiting Exoplanet Survey Satellite mission was designed to find transiting planets around bright, nearby stars. Here, we present the detection and mass measurement of a small, short-period (≈4 days) transiting planet around the bright (V = 7.9), solar-type star HD 86226 (TOI-652, TIC 22221375), previously known to host a long-period (∼1600 days) giant planet. HD 86226c (TOI-652.01) has a radius of 2.16 0.08 R ⊕ and a mass of M ⊕, based on archival and new radial velocity data. We also update the parameters of the longer-period, not-known-to-transit planet, and find it to be less eccentric and less massive than previously reported. The density of the transiting planet is 3.97 g cm-3, which is low enough to suggest that the planet has at least a small volatile envelope, but the mass fractions of rock, iron, and water are not well-constrained. Given the host star brightness, planet period, and location of the planet near both the "radius gap"and the "hot Neptune desert,"HD 86226c is an interesting candidate for transmission spectroscopy to further refine its composition

A pair of tess planets spanning the radius valley around the nearby mid-m dwarf ltt 3780

We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, V = 13.07, K s = 8.204, R s = 0.374 R o˙, M s = 0.401 M o˙, d = 22 pc). The two planet candidates are identified in a single Transiting Exoplanet Survey Satellite sector and validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of P b = 0.77, P c = 12.25 days and sizes r p,b = 1.33 ± 0.07, r p,c = 2.30 ± 0.16 R ⊕, the two planets span the radius valley in period-radius space around low-mass stars, thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 63 precise radial velocity measurements from the High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N, we measure planet masses of mpb 2.62+ 0.48 and-0.46= mpc 8.6+1.6-1.3 M⊕, which indicates that LTT 3780b has a bulk composition consistent with being Earth-like, while LTT 3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and core-powered mass-loss models. The brightness and small size of LTT 3780, along with the measured planetary parameters, render LTT 3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley

Kaon Content of Three-Prong Decays of the Tau Lepton

We present a series of measurements involving the production of charged kaons in three-prong hadronic decays of the {tau} lepton. The data sample was obtained with the TPC/Two-Gamma detector facility at PEP. We set a limit on the branching fraction BR({tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sup {minus}}K{sup 0}) < 0.26% at the 95% confidence level. The process {tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sup {minus}}K{sup 0} is related via SU(3) to the second-class current decay {tau}{sup {minus}} {yields} {nu}{sub {tau}}{pi}{sup {minus}}{eta}. We also present new measurements of the three-prong branching fractions BR({tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sup {minus}}{pi}{sup +}{pi}{sup {minus}} + neutrals) = 0.70 (+0.20/{minus}0.17)% and BR({tau}{sup {minus}} {yields} {nu}{sub {tau}}K{sup {minus}}K{sup +}{pi}{sup {minus}} + neutrals) = 0.16 (+0.10/{minus}0.07)%. 68 refs., 29 figs., 15 tabs

Muon energy loss at high energy and implications for detector design

We study the effects of energy loss and associated electromagnetic showers on muon tracking and momentum measurement in muon detectors operating in the energy range 100 GeV-5 TeV. A detailed Monte Carlo simulation tracks muons and shower particles through a detector structure and evaluates the charged-particle environment in chambers. We find that catastrophic energy loss events accompanied by energetic showers can pose serious problems to designers of muon spectrometers. 14 refs., 6 figs