It has been understood since 1897 that accelerating charges must emit electromagnetic radiation. Although first derived in 1904, cyclotron radiation from a single electron orbiting in a magnetic ...field has never been observed directly. We demonstrate single-electron detection in a novel radio-frequency spectrometer. The relativistic shift in the cyclotron frequency permits a precise electron energy measurement. Precise beta electron spectroscopy from gaseous radiation sources is a key technique in modern efforts to measure the neutrino mass via the tritium decay end point, and this work demonstrates a fundamentally new approach to precision beta spectroscopy for future neutrino mass experiments.
This paper contrasts the natural and anthropogenic controls on the conversion of unreactive N2to more reactive forms of nitrogen (Nr). A variety of data sets are used to construct global N budgets ...for 1860 and the early 1990s and to make projections for the global N budget in 2050. Regional N budgets for Asia, North America, and other major regions for the early 1990s, as well as the marine N budget, are presented to highlight the dominant fluxes of nitrogen in each region. Important findings are that human activities increasingly dominate the N budget at the global and at most regional scales, the terrestrial and open ocean N budgets are essentially disconnected, and the fixed forms of N are accumulating in most environmental reservoirs. The largest uncertainties in our understanding of the N budget at most scales are the rates of natural biological nitrogen fixation, the amount of Nr storage in most environmental reservoirs, and the production rates of N2by denitrification.
New data are reported from a second run of the 2-liter PICO-2L C sub(3) F sub(8) bubble chamber with a total exposure of 129 kg-days at a thermodynamic threshold energy of 3.3 keV. These data show ...that measures taken to control particulate contamination in the superheated fluid resulted in the absence of the anomalous background events observed in the first run of this bubble chamber. One single nuclear-recoil event was observed in the data, consistent both with the predicted background rate from neutrons and with the observed rate of unambiguous multiple-bubble neutron scattering events. The chamber exhibits the same excellent electron-recoil and alpha decay rejection as was previously reported. These data provide the most stringent direct detection constraints on weakly interacting massive particle (WIMP)-proton spin-dependent scattering to date for WIMP masses <50GeV/c super(2).
Study of γγ→γψ(2S) at Belle Wang, X. L.; Aihara, H.; Asner, D. M. ...
Physical review. D,
06/2022, Letnik:
105, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Using 980 fb-1 of data at and around the Υ(nS)(n = 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e+e- collider, the two-photon process γγ → γψ(2S) is ...studied from the threshold to 4.2 GeV for the first time. Two structures are seen in the invariant mass distribution of γψ(2S): one at MR1 = 3922.4 ± 6.5 ± 2.0 MeV/c2 with a width of ΓR1 = 22 ± 17 ± 4 MeV, and another at MR2 = 4014.3 ± 4.0 ± 1.5 MeV/c2 with a width of ΓR2 = 4 ± 11 ± 6 MeV; the signals are parametrized with the incoherent sum of two Breit- Wigner functions. The first structure is consistent with the X(3915) or the χc2(3930), and the local statistical significance is determined to be 3.1σ with the systematic uncertainties included. The second matches none of the known charmonium or charmonium like states, and its global significance is determined to be 2.8σ including the look-elsewhere effect. The production rates are Γγγ B(R1 → γψ(2S)) = 9.8 ± 3.6 ± 1.2 eV assuming (JPC, |λ|) = (0++, 0) or 2.0 ± 0.7 ± 0.2 eV with (2++, 2) for the first structure and Γγγ B(R2 → γψ(2S)) = 6.2 ± 2.2 ± 0.8 eV with (0++, 0) or 1.2 ± 0.4 ± 0.2 eV with (2++, 2) for the second one. Furthermore, the first errors are statistical and the second systematic, and λ is the helicity.
This paper presents a search for the rare flavor-changing neutral current process B0→K*0τ+τ- using data taken with the Belle detector at the KEKB asymmetric energy $e^+$$e^-$ collider. The analysis ...is based on the entire $\Upsilon$$(4S)$ resonance data sample of $711$ $\mathrm{fb}^{-1}$, corresponding to $772 × 10^6$$B$$\bar{B}$ pairs. In our search we fully reconstruct the companion $B$ meson produced in the process $e^+$$e^-$ → $\Upsilon$$(4S)$ → $B$$\bar{B}$ from its hadronic decay modes and look for the decay B0→K*0τ+τ- in the rest of the event. No evidence for a signal is found. We report an upper limit on the branching fraction $\mathscr{B}$(B0→K*0τ+τ-) < $3.1 × 10^{-3}$ at 90% confidence level. This is the first direct limit on $\mathscr{B}$(B0→K*0τ+τ-).
The first simultaneous determination of the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ub}$ using inclusive and exclusive decays is performed with the full Belle data set at ...the $\Upsilon(4S)$ resonance, corresponding to an integrated luminosity of 711 fb^{-1}$. We analyze collision events in which one $B$ meson is fully reconstructed in hadronic modes. This allows for the reconstruction of the hadronic $X_u$ system of the semileptonic $b \to u \ell \bar \nu_\ell$ decay. We separate exclusive $B \to \pi \, \ell\, \bar \nu_{\ell}$ decays from other inclusive $B \to X_u \, \ell\, \bar \nu_{\ell}$ and backgrounds with a two-dimensional fit, that utilizes the number of charged pions in the $X_u$ system and the four-momentum transfer $q^2$ between the $B$ and $X_u$ system. Combining our measurement with information from lattice QCD and QCD calculations of the inclusive partial rate as well as external experimental information on the shape of the $B \to \pi \, \ell\, \bar \nu_{\ell}$ form factor, we determine $\left|V_{ub}^{\mathrm{excl.}} \right| = (3.78 \pm 0.23 \pm 0.16 \pm 0.14)\times 10^{-3}$ and $\left|V_{ub}^{\mathrm{incl.}} \right| = (3.88 \pm 0.20 \pm 0.31 \pm 0.09)\times 10^{-3}$, respectively, with the uncertainties being the statistical error, systematic errors, and theory errors. The ratio of $\left|V_{ub}^{\mathrm{excl.}} \right| / \left|V_{ub}^{\mathrm{incl.}} \right| = 0.97 \pm 0.12$ is compatible with unity.
We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different ...fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a 558 fb-1 data sample collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
We study the decay B+→K+K– π+ and investigate the angular distribution of K+K– pairs with invariant mass below 1.1 GeV / c2. This region exhibits both a strong enhancement in signal and very large ...direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of MK+K– and the differential branching fractions in bins of MK+π–. The results are based on a data sample that contains 772 × 106 $B\bar{B}$ pairs collected at the $Υ$(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e– collider. The result favors the presence of S- and D-waves in low MK+K– region to the detriment of a P-wave.
Review of Particle Physics Workman, R L; Klempt, E; Agashe, K ...
Progress of theoretical and experimental physics,
08/2022, Letnik:
2022, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Abstract
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured ...properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on Machine Learning, and one on Spectroscopy of Light Meson Resonances.
The Review is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings.
The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app.
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