6062 research outputs found
Sort by
Implications of an enhanced <math display="inline"><mrow><mi>B</mi><mo stretchy="false">→</mo><mi>K</mi><mi>ν</mi><mover accent="true"><mrow><mi>ν</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow></math> branching ratio
No full textRare decays mediated by b→sνν¯ transitions have been reported by the Belle II experiment. The branching ratio of the decay B+→K+νν¯ is found to be enhanced with respect to the standard model value. If taken at face value, the implications are profound; either lepton flavor universality is violated at the (multi)-TeV-scale, or light new physics is involved. This holds in general if B(B+→K+νν¯) exceeds 1.2×10-5(1.3×10-5) at 1σ (2σ), which tightens with a decreasing upper limit on B(B→K*νν¯), that is in reach of the Belle II experiment. In view of the strong constraints on electron-muon universality violation in |Δb|=|Δs|=1 processes, viable explanations are heavy, (5–10)-TeV tree-level new physics mediators that couple only to tau-flavors, or lepton flavor violating ones. In addition, couplings of similar size to both left- and right-handed quarks are generically required, implying nonminimal beyond the standard model sectors which are carefully balanced against flavor constraints. The decay Bs0→invisibles can shed light on whether new physics is light or heavy. In the former case, branching ratios can be as large as 10-5
The unitary Fermi gas at large charge and large N
No full textWe study the unitary Fermi gas in a harmonic trapping potential starting from a microscopic theory in the limit of large charge and large number of fermion flavors N. In this regime, we present an algorithmic procedure for extracting data from perturbation theory, order-by-order, without the need for other assumptions. We perform a gradient expansion in the interior of the particle cloud, sufficiently far from the cloud edge where the particle density drops rapidly to zero. In this latter region we present the first microscopic computation characterizing the contribution of the edge terms. The microscopic theory reproduces the predictions of the superfluid eft, including the action, the form of the gap equation, and the energy of the system in a harmonic trap (which maps, via the non-relativistic state-operator correspondence, to the scaling dimension of the lowest operator of charge Q). We additionally give the Wilsonian coefficients at leading order in N up to nnlo in the large-charge expansion
True muonium resonant production at e e colliders with standard crossing angle
No full textTrue muonium (TM) (μμ) is the heaviest and smallest bound state not containing hadrons, after TM (ττ) and mu-tauonium (μτ). One of the proposed methods to observe the spin 1 fundamental state of TM, which has the smallest lifetime among TM spin 1 states, was to build an ee collider with a large crossing angle (θ ∼ 30°) in order to provide TM with a large boost and detect its decay vertex in ee. The following paper will instead show that TM excited states can be observed in relatively large quantities ((10)/month) at a ee collider with standard crossing angle, after setting their center-of-mass energy to the TM mass (∼2m = 211.4 MeV)
Vector-like symmetries and parity conservation in gauge theories with Yukawa couplings
No full textNon-perturbative results in QCD-like theories can be derived employing positivity of the Euclidean path integral measure, as pioneered by Weingarten, Vafa, and Witten. We show that positivity of the measure can be generalized to parity-invariant theories with Yukawa couplings to fundamental scalars, provided the fermions are Dirac and carry a real representation of the gauge group. This result allows us to demonstrate the conservation of parity and vector-like flavor symmetries in such theories, as well as to derive exact inequalities among hadrons' masses
Probing the photon emissivity of the quark-gluon plasma without an inverse problem in lattice QCD
No full textThe thermal photon emissivity of the quark-gluon plasma is determined by the in-medium spectral function of the electromagnetic current at lightlike kinematics, σ(ω). In this work, we present the first lattice QCD results on moments of σ(ω)/ω, defined by the weight function 1/(ω2+(2πTn)2), n∈Z and computed without encountering an inverse problem. We employ two dynamical flavors of O(a)-improved Wilson fermions at a temperature T≈250 MeV and perform the continuum limit. We compare our results for the first two moments to those obtained dispersively by integrating over the spectral function computed at weak coupling by Arnold, Moore and Yaffe
Toward numerical-relativity informed effective-one-body waveforms for dynamical capture black hole binaries
No full textDynamical captures of black holes may take place in dense stellar media due to the emission of gravitational radiation during a close passage. Detection of such events requires detailed modeling, since their phenomenology qualitatively differs from that of quasicircular binaries. Very few models can deliver such waveforms, and none includes information from numerical relativity (NR) simulations of nonquasicircular coalescences. In this study we present a first step towards a fully NR-informed effective-one-body (EOB) model of dynamical captures. We perform 14 new simulations of single and double encounter mergers, and use this data to inform the merger-ringdown model of the TEOBResumS-Dalì approximant. We keep the initial energy approximately fixed to the binary mass, and vary the mass-rescaled, dimensionless angular momentum in the range (0.6, 1.1), the mass ratio in (1, 2.15), and aligned dimensionless spins in (-0.5,0.5). We find that the model is able to match NR to 97%, improving previous performances, without the need of modifying the baseline template. Upon NR informing the model, this improves to 99% with the exception of one outlier corresponding to a direct plunge. The maximum EOB/NR phase difference at merger for the uninformed model is of 0.15 radians, which is reduced to 0.1 radians after the NR information is introduced. We outline the steps towards a fully informed EOB model of dynamical captures, and discuss future improvements
Induced circular polarization on photons due to interaction with axion-like particles in rotating magnetic field of neutron stars
No full textWe investigate how the photon polarization is affected by the interaction with axion-like particles (ALPs) in the rotating magnetic field of a neutron star (NS). Using quantum Boltzmann equations the study demonstrates that the periodic magnetic field of millisecond NSs enhances the interaction of photons with ALPs and creates a circular polarization on them. A binary system including an NS and a companion star could serve as a probe. When the NS is in front of the companion star with respect to the earth observer, there is a circular polarization on the previously linearly polarized photons as a result of the interaction with ALPs there. After a half-binary period, the companion star passes in front of the NS, and the circular polarization of photons disappears and changes to linear. The excluded parameter space for a millisecond NS with 300 Hz rotating frequency, highlights the coupling constant of 1.7 × 10 GeV ≤ gaγγ ≤ 1.6 × 10 GeV for the ALP masses in the range of 7 × 10 eV ≤ ma ≤ 1.5 × 10 eV
Environmental radon control in the 700 m underground laboratory at JUNO
No full textThe Jiangmen Underground Neutrino Observatory is constructing the world's largest liquid scintillator detector, with a 20 kt target mass and approximately 700 m of overburden. The total underground space of civil construction is around 300,000 m, with the main hall comprising about 120,000 m, making it the largest experimental hall in the world. Maintaining a low radon concentration in the underground air is crucial for both human health and the accuracy of experiments involving rare decay detection, such as neutrino and dark matter experiments. To ensure human health and the integrity of neutrino physics experiments, the nominal radon concentration in the main hall must be kept below 200 Bq/m with a maximum value below 400 Bq/m. Introduction of fresh air from above ground can significantly lower radon concentration. A benchmark experiment conducted in the refuge room near the main hall revealed that the radon emanating from underground water is a significant source of radon in the underground air. The total underground ventilation rate is approximately 160,000 m/h of fresh air with about 30 Bq/m^3^{222}Rn from the bottom of the vertical tunnel after the installation of powerful fans. Of this, 55,000 m/h is used for ventilation in the main hall. As a result of these measures, the radon concentration inside the main hall has decreased from 1600 Bq/m to below 200 Bq/m under stable working conditions, with exceptions during rare adverse weather events or fan failures. The employed strategies to control radon concentration in the underground air are described in this paper
The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and Its Implications for Structure Growth
No full textWe present new measurements of cosmic microwave background (CMB) lensing over 9400 deg of the sky. These lensing measurements are derived from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) CMB data set, which consists of five seasons of ACT CMB temperature and polarization observations. We determine the amplitude of the CMB lensing power spectrum at 2.3% precision (43σ significance) using a novel pipeline that minimizes sensitivity to foregrounds and to noise properties. To ensure that our results are robust, we analyze an extensive set of null tests, consistency tests, and systematic error estimates and employ a blinded analysis framework. Our CMB lensing power spectrum measurement provides constraints on the amplitude of cosmic structure that do not depend on Planck or galaxy survey data, thus giving independent information about large-scale structure growth and potential tensions in structure measurements. The baseline spectrum is well fit by a lensing amplitude of A = 1.013 ± 0.023 relative to the Planck 2018 CMB power spectra best-fit ΛCDM model and A = 1.005 ± 0.023 relative to the ACT DR4 + WMAP best-fit model. From our lensing power spectrum measurement, we derive constraints on the parameter combination of from ACT DR6 CMB lensing alone and when combining ACT DR6 and Planck NPIPE CMB lensing power spectra. These results are in excellent agreement with ΛCDM model constraints from Planck or ACT DR4 + WMAP CMB power spectrum measurements. Our lensing measurements from redshifts z ∼ 0.5–5 are thus fully consistent with ΛCDM structure growth predictions based on CMB anisotropies probing primarily z ∼ 1100. We find no evidence for a suppression of the amplitude of cosmic structure at low redshifts
Detector Development for the CRESST Experiment
No full textRecently low-mass dark matter direct searches have been hindered by a low-energy background, drastically reducing the physics reach of the experiments. In the CRESST-III experiment, this signal is characterised by a significant increase of events below 200 eV. As the origin of this background is still unknown, it became necessary to develop new detector designs to reach a better understanding of the observations. Within the CRESST collaboration, three new different detector layouts have been developed, and they are presented in this contribution