Search

We analyzed how to test flavor and helicity structures of the corresponding amplitudes in view of future data, motivated by the recent hints of lepton flavor universality violation observed in semileptonic B decays. The general assumption that non-standard effects are controlled by a U(2)5 flavor symmetry, minimally broken as in the Standard Model Yukawa sector, leads to stringent predictions on leptonic and semileptonic B decays. Future measurements will allow to prove or falsify this general hypothesis independently of its dynamical origin. [ABSTRACT FROM AUTHOR]

The persistent discrepancy of about 3.5 standard deviations between the experimental measurement and the Standard Model prediction for the muon anomalous magnetic moment, aµ, is one of the most promising hints for the possible existence of new physics. Here we report on our lattice QCD calculation of the hadronic vacuum polarisation contribution a μ hvp $ a_\mu ^{{\rm{hvp}}} $ , based on gauge ensembles with Nf = 2 + 1 flavours of O(a) improved Wilson quarks. We address the conceptual and numerical challenges that one encounters along the way to a sub-percent determination of the hadronic vacuum polarisation contribution. The current status of lattice calculations of a μ hvp $ a_\mu ^{{\rm{hvp}}} $ is presented by performing a detailed comparison with the results from other groups. [ABSTRACT FROM AUTHOR]

We present the current status of the Next-to-Next-to-Leading Order QED contribution to the µescattering. Particular focus is given to the techniques involved to tackle the virtual amplitude and their automatic implementation. Renormalization of the amplitude will be also discuss in details. [ABSTRACT FROM AUTHOR]

The largest uncertainties in the Standard Model calculation of the anomalous magnetic moment of the muon (g−2)µ come from hadronic effects, namely hadronic vacuum polarization (HVP) and hadronic lightby-light (HLbL) contributions. Especially the latter is emerging as a potential roadblock for a more accurate determination of (g−2)µ. The main focus here is on a novel dispersive description of the HLbL tensor, which is based on unitarity, analyticity, crossing symmetry, and gauge invariance. This opens up the possibility of a data-driven determination of the HLbL contribution to (g−2)µ with the aim of reducing model dependence and achieving a reliable error estimate. Our dispersive approach defines unambiguously the pion-pole and the pion-box contribution to the HLbL tensor. Using Mandelstam double-spectral representation, we have proven that the pion-box contribution coincides exactly with the one-loop scalar-QED amplitude, multiplied by the appropriate pion vector form factors. Using dispersive fits to high-statistics data for the pion vector form factor, we obtain α μ π -box = − 15.9 (2) × 10 − 11 $ \alpha _\mu ^{\pi {\rm{ - box}}} = - 15.9(2) \times {10^{ - 11}} $. A first model-independent calculation of effects of ππ intermediate states that go beyond the scalar-QED pion loop is also presented. We combine our dispersive description of the HLbL tensor with a partial-wave expansion and demonstrate that the known scalar-QED result is recovered after partial-wave resummation. After constructing suitable input for the γ*γ* → ππ helicity partial waves based on a pion-pole left-hand cut (LHC), we find that for the dominant charged-pion contribution this representation is consistent with the two-loop chiral prediction and the COMPASS measurement for the pion polarizability. This allows us to reliably estimate S-wave rescattering effects to the full pion box and leads to α μ π -box + α μ , J = 0 π π , π -pole   LHC = − 24 (1) × 10 − 11 $ \alpha _\mu ^{\pi {\rm{ - box}}} + \alpha _{\mu ,J = 0}^{\pi \pi ,\pi {\rm{ - pole}}\,{\rm{LHC}}} = - 24(1) \times {10^{ - 11}} $. [ABSTRACT FROM AUTHOR]

The decay K + → π + v v ¯ $ {K^ + } \to {\pi ^ + }v\bar v $ , with a very precisely predicted branching ratio of less than 10−10 in the Standard Model framework, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at CERN SPS is designed to measure the branching ratio of such decay with a decay-in-flight technique, novel for this channel. The main goal of NA62 is to measure such Branching Ratio of K + → π + v v ¯ $ {K^ + } \to {\pi ^ + }v\bar v $ with an accuracy better than 20%. This will be achieved by collecting up to 100 K + → π + v v ¯ $ {K^ + } \to {\pi ^ + }v\bar v $ events with a background contamination at the level of 10%. The NA62 detector was commissioned in 2014 and 2015 and the experiment took physics data from 2015 to 2018. NA62 has already published the result of the 2016 data analysis. The 2017 data analysis is in progress, the single event sensitivity reached and the evaluation of the main backgrounds will be shown in this contribution. [ABSTRACT FROM AUTHOR]

The MEG experiment has recently set a new upper limit on the branching ratio of the µ+ → e+γ decay, ℬ(µ+ → e+γ) < 4.2 × 10−13 (at 90% confidence level) and un upgrade of the experiment (the MEGII experiment) is ongoing with the aim of improving the single event sensitivity (SES) by one order of magnitude with respect to the previous MEG experiment's SES. The strong scientific motivation associated with the charged Lepton Flavour Violation (cLFV) searches pushes also towards searching for the complementary muon cLFV µ+ → e+e+e− decay with a completely new apparatus, the Mu3e experiment, aiming at a SES improved by at least three orders of magnitude with respect to the previous SINDRUM experiment's SES (Mu3e phase I). An ultimate SES of few ×10−16 is foreseen requiring 109 µ/s (Mu3e phase II). Both experiments will be hosted at the Paul Scherrer Institut which currently delivers the most intense continuous low energy muon beam in the world up to few ×108 µ/s. The status of both the MEGII and Mu3e phase I experiments is given. [ABSTRACT FROM AUTHOR]

The Mu2e experiment aims to improve, by four orders of magnitude, current sensitivity in the search for the charged-lepton flavor violating (cLFV) neutrino-less conversion of a negative muon into an electron. The conversion process will be identified by a distinctive signature of a mono-energetic electron with energy slightly below the muon rest mass. In the Standard Model this process has a negligible rate. However, in many Beyond the Standard Model scenarios its rate is within the reach of Mu2e sensitivity. In this paper, we explain the Mu2e design guidelines and summarize the status of the experiment. [ABSTRACT FROM AUTHOR]

The 4-loop contribution to the slope of the Dirac form factor in QED has been evaluated with 1100 digits of precision. The value is m 2 F 1 (4) ′ (0) = 0.886545673946443145836821730610315359390424032660064745 ⋯ (α π) 4 $ {m^2}F_1^{(4)'}(0) = {\rm{0}}{\rm{.886545673946443145836821730610315359390424032660064745}} \cdots {\left({{\alpha \over \pi }} \right)^4} $. We have also obtained a semi-analytical fit to the numerical value. The expression contains harmonic polylogiπ2iπ iπ arithms of argument e i π 3 , e 2 i π 3 , e i π 2 $ {e^{{{i\pi } \over 3}}},{e^{{{2i\pi } \over 3}}},{e^{{{i\pi } \over 2}}} $ , one-dimensional integrals of products of complete elliptic integrals and six finite parts of master integrals, evaluated up to 4800 digits. We show the correction to the energy levels of the hydrogen atom due to the slope. [ABSTRACT FROM AUTHOR]

I summarize recent experimental results for two photon production of mesons. These processes include the neutral pion, η and η′ transition form factors and two photon production of pseudoscalar meson pairs. In addition I discuss the related hadronic and radiative processes. All these processes are attracting attention of experiment and theory due their relevance for the hadronic light-by-light contribution to the muon anomalous magnetic moment. [ABSTRACT FROM AUTHOR]

Searches for permanent electric dipole moments of fundamental particles and systems with spin are the experiments most sensitive to new CP violating physics and a top priority of a growing international community. We briefly review the current status of the field emphasizing on the charged leptons and lightest baryons. [ABSTRACT FROM AUTHOR]

The 3π-channel contribution to hadronic vacuum polarization (HVP) in the anomalous magnetic moment of the muon (g−2)µ is examined based on a dispersive representation of the γ* → 3π amplitude. This decay amplitude is reconstructed from dispersion relations, fulfilling the low-energy theorem of QCD. The global fit function is applied to the data sets of the 3π channel below 1.8 GeV, which constitutes the secondlargest exclusive contribution to HVP and its uncertainty. The dominant ωand φ-peak regions in the e+e− → 3π cross section as well as the non-resonant regions are precisely described to obtain our best estimate. The final result, a μ 3 π | ≤ 1.8   GeV   =   46.2(6)(6) × 10 − 10 $ a_\mu ^{3\pi }\left| { \le 1.8\,{\rm{GeV}}\,{\rm{ = }}\,{\rm{46}}{\rm{.2(6)(6)}} \times {\rm{1}}{{\rm{0}}^{ - 10}}} \right. $ , reduces the model dependence owing to the fundamental principles of analyticity and unitarity and provides a cross check for the compatibility of the different e+e− → 3π data sets. A combination of the current analysis and the recent similar treatment of the 2π channel yields a dispersive determination of almost 80% of the entire HVP contribution. Our analysis reaffirms the muon anomaly at 3.4σ level, when the rest of the contributions is taken from the literature. [ABSTRACT FROM AUTHOR]

I review the physics case for flavour violating axions. In particular, I argue that relaxing the assumption of the universality of the Peccei-Quinn current opens up new pathways, including: the relaxation of the Supernova bound on the axion mass, a possible connection with the Standard Model flavour puzzle and the experimental opportunity of discovering the axion via flavoured axion searches. [ABSTRACT FROM AUTHOR]

Tests of lepton flavour universality in B decays offer an excellent opportunity to test the Standard Model, and show hints of new physics in analyses performed by the LHCb, Belle and BaBar experiments. Several theoretical models proposed to explain possible violation of lepton flavour universality claim a connection with lepton flavour violation in B decays. These proceedings review the experimental status of the tests of lepton flavour universality and the searches of lepton flavour violation in B decays. [ABSTRACT FROM AUTHOR]

The discovery of the Higgs boson has fully confirmed the Standard Model of particles and fields. Nevertheless, there are still fundamental phenomena, like the existence of dark matter, the neutrino masses and the baryon asymmetry of the Universe, which deserve an explanation that could come from the discovery of new particles. The SHiP experiment at CERN is proposed to search for very weakly coupled particles in the few GeV mass domain where the existence of such particles is largely unexplored. A beam dump facility using high intensity 400 GeV protons is a copious source of such unknown particles in the GeV mass range. The beam dump is also a very intense source of neutrinos and, in particular, of tau neutrinos, the less known particle in the Standard Model. We report the physics potential of such an experiment. An ancillary measurement of the charm cross-section was carried out in July 2018 and the data are under analysis and we report preliminary results. Moreover, a prototype of the neutrino detector is being designed to possibly take data at the LHC in its Run3 of operation. We describe the proposed detector and the physics case. [ABSTRACT FROM AUTHOR]

We discuss how holographic models of QCD are used to study the the hadronic light-by-light (HLbL) scattering amplitude contribution to the muon anomalous magnetic moment. After a brief description of the various models, we focus on a particular one, introduced by Hirn and Sanz, emphasizing the role it assigns to the pion, and the vector and-axial vector resonances. We review how the parameters of the model are fixed by imposing condition on the low energy and the deep Euclidean limit of two-point correlators of QCD vector and axial vector currents. We then focus on the evaluation of the three-point axial-vector-vector current correlator and the pion anomalous transition form factor to be used in the one-pion exchange HLbL diagram and study its asymptotic properties. Finally, we present preliminary results on the four vector current correlator that defines the Hadronic Light-by-Light tensor. We find that axial-vector resonances play an important rule in recovering the correct asymptotic behaviour predicted by QCD at large Euclidean momenta. [ABSTRACT FROM AUTHOR]

High-precision measurements of the proton radius via scattering, electric hydrogen spectroscopy and muonic hydrogen spectroscopy do not agree on the level of more than 5 σ. This proton radius puzzle persists now for almost a decade. This paper gives a short summary over the progress in the solution of the puzzle as well as an overview over the planned experiments to finally solve this puzzle at the interface of atomic and nuclear physics. [ABSTRACT FROM AUTHOR]

Fermilab is collaborating with Lawrence Berkeley National Laboratory (LBNL) and Brookhaven National Laboratory (BNL) (US-LARP collaboration) to develop a large-aperture Nb3Sn superconducting quadrupole for the Large Hadron Collider (LHC) luminosity upgrade. An important component of this work is the development of materials that are sufficiently radiation resistant for use in critical areas of the upgrade. This paper describes recent progress in characterization of materials, including the baseline CTD101K epoxy, cyanate ester blends, and Matrimid 5292, a bismaleimide-based system. Structural properties of "ten stacks" of cable impregnated with these materials are tested at room and cryogenic temperatures and compared to the baseline CT-101K. Experience with potting 1 and 2 meter long coils with Matrimid 5292 are described. Test results of a single 1-m coil impregnated with Matrimid 5292 are reported and compared to similar coils impregnated with the traditional epoxy. [ABSTRACT FROM AUTHOR]

The Muon-to-Electron conversion experiment (Mu2e), under development at Fermilab, seeks to detect direct muon to electron conversion to provide evidence for a process violating muon and electron lepton number conservation that cannot be explained by the Standard Model of particle physics. The required magnetic field is produced by a series of superconducting solenoids. This paper describes the conceptual design of the 5 T, 4 m long solenoid cold mass with 1.67 m bore with the emphasis on the magnetic, radiation and thermal analyses. [ABSTRACT FROM AUTHOR]

Fermilab is developing Nb3Sn quadrupole magnets for the planned upgrade of interaction regions of the Large Hadron Collider (LHC). Two distinctly different approaches have been employed, one using quadrupole-symmetric and one using dipole-symmetric collar laminations. This paper describes the design features of both collar types, collaring techniques for brittle Nb3Sn coils, and compares the advantages and disadvantages of the two approaches. Results of mechanical analysis for quadrupoles based on dipole-type and quadrupole-type collars are presented. Magnet construction issues and test results are reported. Test results include coil and component strain measurements during construction. Plans for the completion and test of the first dipole-symmetric assembly are described. [ABSTRACT FROM AUTHOR]

This is an overview of recent developments and future prospects in the search for dark matter and new physics with astronomical and astro-particle techniques. [ABSTRACT FROM AUTHOR]

A series of 1-m long Nb3Sn dipole magnets have been built at Fermilab in an attempt to refine the wind-and-react technology for Nb3Sn conductor. Models have been made with MJR and PIT strand with varying degrees of success. Subsequently two new dipole “mirror” magnets based on RRP Nb3Sn coils were constructed and tested. This paper describes the design, fabrication and test results of those magnets. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fermilab is involved in the development of Nb3Sn magnets for future hadron colliders. One of the magnet design options is based on cosine-theta coils and the wind-and-react approach. Three short dipole models of this type were fabricated and tested revealing serious problems in magnet quench performance. To effectively address these issues, coil tests were continued in a mirror magnet configuration, where one coil was replaced with a half-cylinder of low carbon steel (the magnetic mirror) inside the magnet mechanical structure. This approach has reduced the fabrication cost and time as well as improved the coil instrumentation. The paper summarizes the magnetic and mechanical design of mirror magnet configuration along with fabrication details. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fermilab is developing 10-12 T superconducting dipole magnets for future accelerators based on Nb[sub 3]Sn conductor. Within the High Field Magnet Project, a common coil design was chosen for magnet R&D using the react & wind approach. Based on cable studies in which a variety of designs were tried and tested using inexpensive ITER strands, a 41-strand cable was used for a racetrack coil, whereas a 60-strand cable was preferred for the common coil model. Multifilamentary Nb[sub 3]Sn strands 0.7 mm in diameter to be respectively used in the racetrack coil and the common coil model were purchased from OST (Modified Jelly Roll technology) and IGC (Internal Tin technology). They are herein characterized by I[sub c], n-value, residual resistivity ratio, and magnetization. Results of cabling and bending degradation are also presented. [ABSTRACT FROM AUTHOR]