Search

Heavy-quark spin-symmetry (HQSS) partners of the isovector bottomonium like states Zb(10610) and Zb(10650) are predicted within the molecular picture. Treating both Zb's as shallow bound states, we solve the system of coupled-channel integral equations for the contact plus one-pion exchange (OPE) potentials to predict the location of the partner states with the quantum numbers J++ (J = 0,1,2). In particular, we predict the existence of a narrow tensor 2++ state residing a few MeV below the B∗B¯∗ threshold. It is emphasised that the tensor part of the OPE potential in combination with HQSS breaking due to the nonvanishing B∗ -B mass splitting has a significant impact on the location of this partner state. [ABSTRACT FROM AUTHOR]

The Monte Carlo event generator BabaYaga has been developed for high precision simulation of QED processes (e+e−→ e+e− , e+e−→ µ+µ− and e+e−→ γγ) at flavour factories, chiefly for luminometry purposes, with an estimated theoretical accuracy at the 0.1% level or better. QED radiative corrections are included by means of a Parton Shower in QED matched with exact next-to-leading order corrections to reach the required accuracy. The latter is assessed by means of consistent comparisons to independent calculations and an estimate of the size of missing higher-order corrections. The main theoretical framework is overviewed and the status of the generator is summarized. [ABSTRACT FROM AUTHOR]

We report the status and progress of the Heavy Flavour Averaging Group work on the global fit of τ tau lepton branching fractions, on the lepton universality tests and on the measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vus| using τ lepton measurements. We also review the prospects for improving the precision of the |Vus| measurement. [ABSTRACT FROM AUTHOR]

Jefferson Laboratory is finishing a major upgrade and has already started operations with the 12 GeV continuous electron beam. The main research direction is the study of the structure of hadrons, including a search for gluon excitations in the spectra of light mesons and baryons, and studies of multidimensional images of the nucleon. Studied of certain properties of atomic nuclei are also ongoing. There is also an active program of searching for effects beyond the Standard Model in parity-violating electron scattering, as well as a search for new particles. [ABSTRACT FROM AUTHOR]

Large data amount, about 1 ab−1 of integrated luminosity, collected in experiments with the Belle detector provided a good possibilities for precise measurements of the hadronic cross sections in e+e− annihilation. Main results obtained in this field with the Belle detector as well as perspectives of the new experiments with the Belle II detector at the SuperKEKB collider is discussed in this report. [ABSTRACT FROM AUTHOR]

Two-photon decays of a tensor D∗D¯∗ molecule are studied and the suggested approach is applied to the X(3915) charmonium-like state under the assumption of the latter being a 2++ molecule — a spin partner of the X(3872). It is argued that the existing experimental data disfavour such an identification of this state. Therefore, it is suggested that either the X(3915) has a different exotic nature or it has to be identified as a scalar. [ABSTRACT FROM AUTHOR]

We present results obtained by the KLOE Collaboration at the DAфNE e+e− collider located in Frascati Laboratories, Italy. The results concern precise measurements of several η meson decays such as Dalitz slope parameters and charge asymmetries for η → π + π − π 0 $ \eta \to \mathop \pi \nolimits^ + \mathop \pi \nolimits^ - \mathop \pi \nolimits^0 $ , branching ratio and plane asymmetry for η → π + π − e + e − $ \eta \to \mathop \pi \nolimits^ + \mathop \pi \nolimits^ - \mathop {\rm{e}}\nolimits^ + \mathop {\rm{e}}\nolimits^ - $ , and first observation of η → e + e − e + e − $ \eta \to \mathop {\rm{e}}\nolimits^ + \mathop {\rm{e}}\nolimits^ - \mathop {\rm{e}}\nolimits^ + \mathop {\rm{e}}\nolimits^ - $ along with its branching ratio determination. Also preliminary studies of η → π 0 γ γ $ \eta \to \mathop \pi \nolimits^0 \gamma \gamma $ decay channel are presented as well as physics perspectives for many different processes for the ongoing KLOE−2 data taking. [ABSTRACT FROM AUTHOR]

In recent years data have been accumulated at various experiments about states in the heavy quarkonium mass range that seem to be inconsistent with the most simple variants of the quark model. In this contribution it is demonstrated that most of those data are consistent with a dominant molecular nature of those states. It is also discussed which kind of observables are sensitive to the molecular component and which are not. [ABSTRACT FROM AUTHOR]

The LHCb experiment is optimized to make precision measurements in the flavour sector. The large datasets collected between 2010 and 2016 allow to study the properties of heavy hadrons with unprecedented precision. In these proceedings recent results related to three topics are discussed: studies of charmonium production and properties using inclusive b → φφX decays, the observation of charmed pentaquarks and exotic mesons, and the observation of five new excited Ωc baryons. [ABSTRACT FROM AUTHOR]

An event generator for multi hadron production is presented for measuring the R value in the τ-charm energy region with e+e− collisions. The initial state radiation effects are considered up to second order accuracy, and the radiative correction factor is calculated with hadronic Born cross sections. The established exclusive processes are generated according to their measured cross sections, while the missing processes are generated using the LUND Area Law model, and its parameters are tuned with data collected at s $ \sqrt s $ = 3.08 GeV. The optimized values are validated with data in the range s $ \sqrt s $ = 2.2324 ∼ 3.671 GeV. These optimized parameters are universally valid for event generation below the DD¯threshold. [ABSTRACT FROM AUTHOR]

An overview of the most recent results by BABAR on the search of dark photon and dark sector gauge bosons is presented, with larger emphasis on dark photon decays in invisible channels and searches for muonic dark force. [ABSTRACT FROM AUTHOR]

Belle II experiment at the SuperKEKB collider is a major upgrade of the Belle experiment at the KEKB asymmetric e+e− collider at the KEK. The experiment will focus on the search for new physics beyond the standard model via high precision measurement of heavy flavor decays and search for rare signals. In this talk, we present the status of the SuperKEKB collider and the Belle II detector. [ABSTRACT FROM AUTHOR]

The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today's nuclear physics. In a pursuit of reconciling the puzzle an experiment is underway at MAMI, which exploits the radiative tail of the elastic peak to study the properties of electromagnetic processes and to extract the proton charge form factor ( G E p) $ \left({\mathop G\nolimits_E^p } \right) $ at extremely small Q2. This paper reports on the latest results of the first such measurement performed at the three-spectrometer facility of the A1-Collaboration, which led to a precise validation of radiative corrections far away from elastic line and provided measurements of G E p $ \mathop G\nolimits_E^p $ for 0.001 ≤ Q2 ≤ 0.017 (GeV/c)2. [ABSTRACT FROM AUTHOR]

Recent results of a high-statistics τ lepton studies at B factories are reported. Reviewed are the measurements of Michel parameters in leptonic and radiative leptonic τ decays at Belle, as well as the measurement of the branching fractions of the radiative leptonic τ decays at BABAR. Searches for CP symmetry violation in hadronic decays with K S 0 $ \mathop K\nolimits_S^0 $ are also briefly discussed. [ABSTRACT FROM AUTHOR]

The overview of two running BINP electron-positron colliders VEPP-4M and VEPP-2000 is presented. Since 2016 both colliders are joint to the single accelerator complex via common injector that supplies more intensive beams. In 2017 VEPP-2000 started data taking after 3 years of upgrade. The project of Super-Charm-Tau factory waits for the final government's approval being considered as one of 6 mega-science project in Russia. [ABSTRACT FROM AUTHOR]

This contribution reports on the recent measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e+e− collider BEPCII is a double-ring symmetric collider running at s $ \sqrt s $ between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e+e−-annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the measured e + e − → p − p $ \mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop p\limits^ - p $ cross section and the time-like proton form factor are presented. Preliminary results from the analysis of the initial state radiation process e + e − → p − p γ $ \mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop p\limits^ - p\gamma $ using a data set of 7.408 fb−1 collected at center of mass energies between 3.773 and 4.6 GeV, are also shown. The cross sections for e + e − → Λ c − − Λ c + m a t h 5 − − − − − e + e − → Λ − Λ $ \mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop {\mathop \Lambda \nolimits_c^ - }\limits^ - \mathop \Lambda \nolimits_c^ + $ and e + e − → Λ − Λ $ \mathop e\nolimits^ + \mathop e\nolimits^ - \to \mathop \Lambda \limits^ - \Lambda $ are measured near threshold with unprecedented precision. Preliminary results on the first measurement of the ^c form factor ratio |GE|/|GM| are also given. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different s $ \sqrt s $ are also described. [ABSTRACT FROM AUTHOR]

The two-photon physics program of the BESIII Collaboration is mainly motivated by the need of new measurements of transition form factors as input for the Standard Model calculations of a μ H L b L $ \mathop a\nolimits_\mu ^{HLbL} $ , the hadronic light-by-light scattering contribution to the anomalous magentic moment of the muon. The large data sets acquired at BESIII allow to study the transition form factors of pseudoscalar mesons in the relevant region of momentum transfer for a μ H L b L $ \mathop a\nolimits_\mu ^{HLbL} $. In this presentation the status of the respective measurements for π0,η and η' mesons are discussed, and prospects for studies of multi-meson systems as well as of doubly-virtual transition form factors are given. [ABSTRACT FROM AUTHOR]

Higher-order QED radiative corrections to elastic electron-proton scattering are discussed. It is shown that they are relevant for high-precision experiments on proton form factor measurements. Analytic result are obtained for next-to-leading second order corrections to the electron line. Light pair corrections are taken into account. The role of the hadronic contribution to vacuum polarization is discussed. Numerical results are given for the conditions of the experiment on proton form factors performed by A1 Collaboration. Preliminary results are also shown for the set-up with reconstruction of momentum transfer from the recoil proton momentum. [ABSTRACT FROM AUTHOR]

The pp¯invariant mass spectra in the processes e+e−→ pp¯, e+e−→ nn¯, J/ψ → pp¯ω, J/ψ → pp¯ρ, and J/ψ → pp¯γ close to the pp¯is discussed. The optical potentials for NN¯pair in the superposition of S and D waves (due to tensor forces) at spin unity of the pair, as well as for NN¯pair in the S wave at spin zero of the pair, are proposed. The parameters of the potentials are obtained by fitting the cross sections of NN¯scattering together with the pp¯invariant mass spectra in e+e−→ pp¯annihilation and J/ψ decays. Good agreement with the available experimental data is achieved. Using our potential and the Green's function approach we also describe the cross section of e+e−→ 6π and the η'π+ π− invariant mass spectrum in the decay J/ψ → γη'π+π− in the energy region near the NN¯threshold. [ABSTRACT FROM AUTHOR]

Recent theory results on direct production of resonances with positive charge conjugationin electron-positron annihilation are reviewed. The strong modeldependence is emphasized, with predictions varying between 0.03 eV and 0.43 eV for the charmonium state with JPC = 1++ and between0.16 eV and4.25 eV for the state with JPC =2++. For the state with JPC = 0++ the cross section is of O ( m e 2 / M x 2) $ \left({\mathop m\nolimits_e^2 /\mathop M\nolimits_x^2 } \right) $ and thus negligeable for all practical purpose. The importance of the relative phase of the production amplitude is emphasized. [ABSTRACT FROM AUTHOR]

An update of the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic couplings constant at the Z-boson mass is presented. Newest e+e−→ hadrons cross-section data mainly from the BABAR and VEPP-2000 experiments have been included. For the muon (g−2)/2, the lowest-order hadronic contribution is evaluated to be (693.1 ± 3.4) · 10−10, improving the precision of our previous evaluation by 21%. The full Standard Model prediction differs by 3.5 σ from the experimental value. The five-quark hadronic contribution to α (m z 2) $ \alpha (\mathop m\nolimits_z^2) $ is evaluated to be (276.0 ± 0.9) · 10−4. [ABSTRACT FROM AUTHOR]

The R value is important for muon magnetic moment aµ and QED running coupling constant evaluated at Z pole, is useful to extract resonance parameters. BESIII experiment collected about 130 energy points between 2.0GeV and 4.6GeV for a precise measurement of R value. The status of R measurement at BESIII is reported in this paper. [ABSTRACT FROM AUTHOR]

The KLOE results on the measurement of the transition form factors of the η and π0 mesons in φ Dalitz decays are presented. Also we report in the determination of the Γ(η → γγ) in γγ collisions, for which KLOE has delivered the most precise measurement up to the date. The prospects for γγ physics of the upgraded detector KLOE-2, which is taking data aiming to collect more than 5 fb−1 by March 2018, are reviewed. [ABSTRACT FROM AUTHOR]

Light meson decays are used to investigate topics related to fundamental aspects of particle physics. Precision measurements of meson Dalitz decays give input to theoretical evaluations of the Hadronic Light-by-Light contribution (HLbL) to the anomalous magnetic moment of the muon. The A2 collaboration, using the Crystal Ball/TAPS setup at MAMI, has recently published several high precision results on transition form factors which are related to HLbL. Pseudoscalar η' decays allow for studies of topics like ππ scattering lengths, effective field theories and fundamental symmetries. In 2014 the collaboration had a dedicated experimental campaign with one of its main goals to measure the dynamics of η'→ π0π0η with high precision. A brief overview of the experimental setup, physics motivations, analyses and results are given. [ABSTRACT FROM AUTHOR]

We discuss status and prospects of a dispersive analysis of the π0, η, and η ′ transition form factors. Particular focus is put on the various pieces of experimental information that serve as input to such a calculation. These can help improve on the precision of an evaluation of the light pseudoscalar pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.** [ABSTRACT FROM AUTHOR]

I will report on the recent measurement of the fine structure constant below 1 GeV with the KLOE detector. It represents the first measurement of the running of α(s) in this energy region. Our results show a more than 5σ significance of the hadronic contribution to the running of α(s), which is the strongest direct evidence both in time-and space-like regions achieved in a single measurement. From a fit of the real part of Δα(s) and assuming the lepton universality the branching ratio BR(ω → µ+µ−) = (6.6 ± 1.4stat ± 1.7syst) · 10−5 has been determined [ABSTRACT FROM AUTHOR]

I provide updates for the theoretical predictions of the muon and electron anomalous magnetic moments, for the shift in the fine structure constant α(MZ)and for the weak mixing parameter sin 2 Θ w (M Z) $ \mathop {\sin }\nolimits^2 \mathop \Theta \nolimits_w (\mathop M\nolimits_Z) $. Phenomenological results for Euclidean time correlators, the key objects in the lattice QCD approach to hadronic vacuum polarization, are briefly considered. Furthermore,I present a list of isospin breaking and electromagnetic corrections for the lepton moments, which may be used to supplement lattice QCD results obtained in the isospin limit and without the e.m. corrections. [ABSTRACT FROM AUTHOR]

We briefly review the current status of the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. Based on various model calculations in the literature, we obtain the estimate a μ H L b L = (102 ± 39) × 10 − 11 $ \mathop a\nolimits_\mu ^{HLbL} = (102 \pm 39) \times \mathop {10}\nolimits^{ - 11} $. Recent developments including more model-independent approaches using dispersion relations and lattice QCD, that could lead to a more reliable estimate, are also discussed. [ABSTRACT FROM AUTHOR]

The data sample collected in 2011-2013 at the c.m.s. energies between 0.32-2 GeV with the CMD-3 detector operating at the VEPP-2000 e+e− collider is analzed. The collected data corresponds to an integrated luminosity about ∼ 60pb−1. The techniques for determination of the integrated luminosity for each energy setting is described. Some preliminary results of the study of the processes e+e−→ K+K− + nπ (n = 1,2,3) with two charged kaons in the final state are presented. These processes have several intermediate states, which are important to correctly descript the angular distributions of final particles and the cross sections dependence on the energy. [ABSTRACT FROM AUTHOR]

The reaction e+e−→ π+ π−π0η has been studied in the experiment with the SND detector at the VEPP-2000 e+e− collider. The reaction proceeds via the four intermediate states: ωη, φη, a0ρ, and structureless π+π−π0η state, which may be, for example, ρ(1450) with ρ(1450) → ρ(770)η. The total e+e−→ π+π−π0η cross section and cross section for the four intermediate states have been measured and fitted in the vector meson dominance model. [ABSTRACT FROM AUTHOR]

The CMD-3 detector has been successfully collecting data at the electron-positron collider VEPP-2000 since December 2010. The first scan below 1 GeV for a π+π− measurement was performed in 2013. The collected data sample corresponds to about 18 pb−1 of integrated luminosity in this energy range. Analysis of the e+e−→ π+π− cross section is in progress. Status of this measurement are presented. [ABSTRACT FROM AUTHOR]

Recent SND results on the study of the process e+e−→ π0γ are presented. The study is based on data collected with the SND detector on the VEPP-2M and VEPP-2000 e+e− colliders with an integrated luminosity of 25 and 46 pb−1, respectively. The VEPP-2M data used in this analysis are recorded in the center-of-mass energy range 0.60-1.38 GeV, while the VEPP-2000 data in the range 1.05-2.00 GeV. [ABSTRACT FROM AUTHOR]

Precision measurements of the hadronic cross sections e+e−→ π+ π− , π+π−π0, π+π−2π0, ωπ0 and π+π−3π0 are performed at the BESIII experiment located in Beijing, China. These cross section measurements are needed as input for the Standard Model prediction of the anomalous magnetic moment of the muon, (g − 2)µ.The initial state radiation method is used to access the energy regions of interest for (g − 2)µ. Our results will improve the precision of the Standard Model prediction of (g − 2)µ. [ABSTRACT FROM AUTHOR]

New hadronic cross sections measured by the BABAR experiment are presented: e+e−→ π+π−π0π0, e+e−→ π+π−η, and the kaonic channels e+e−→ KSKLπ0 , KSKLπ0π0 , KSKLη, KSK±π+π0 , KSK±π+η. [ABSTRACT FROM AUTHOR]

At the end of 2016 the SND detector resumed data taking at the upgraded VEPP-2000 e+e− collider. The analysis of data accumulated in 2010-2013 with an integrated lumonosity of 70 pb−1 is continuing. Recent results on measurements of various hadronic cross sections are presented. [ABSTRACT FROM AUTHOR]

The CMD-3 detector is installed at the VEPP-2000 e+e− collider at BINP (Novosibirsk, Russia). It is a general-purpose detector, equipped with a tracking system, two crystal (CSI and BGO) calorimeters, liquid Xe calorimeter, TOF and muon systems. The main goal of experiments at CMD-3 is a study of exclusive modes of e+e−→ hadrons at energies s ≤ 2 $ \sqrt s \le $ GeV. In particular, these results provide an important input for calculation of the hadronic contribution to the muon anomalous magnetic moment. The first round of data taking was performed in 2011–2013, when about 60 1/pb were taken in the center-of-mass (c.m.) energy range from 0.32 to 2.0 GeV. Here we present a survey of results of data analysis. Between 2013 and 2016 the collider and the detector were upgraded. The data taking resumed by the end of 2016. In the first run after the upgrade about 50 1/pb were collected at the energy range between 1.28 and 2.007 GeV. We discuss the upgrade and the first preliminary results from the new data. [ABSTRACT FROM AUTHOR]

We review the four-loop QED corrections to the anomalous magnetic moment of the muon. The fermionic contributions with closed electron and tau contributions are discussed. Furthermore, we report on a new independent calculation of the universal four-loop contribution and compare with existing results. [ABSTRACT FROM AUTHOR]

A key motivation for the two-photon physics program of the BESIII collaboration is the need of high precision data on electromagnetic transition form factors as input to the calculations of the contribution of hadronic Light-by-light scattering to the anomalous magnetic moment of the muon. The data collected with the BESIII detector allow to study the momentum dependence of the form factors at small momentum transfers, which is of special relevance for aμ. In this presentation the ongoing measurements of the transition form factors of π0, η and η' mesons, as well as pion pairs, are discussed, and the potential for first double-tagged measurements at BESIII are pointed out. [ABSTRACT FROM AUTHOR]

There is a long standing discrepancy of 3 – 4 standard deviations between the direct measurement and the Standard Model prediction of the anomalous magnetic moment of the muon (g − 2)μ. While new direct measurements have been proposed to clarify the situation, theory calculations are completely limited by the accuracy of the hadronic contributions to (g − 2)μ. In order to increase their precision, experimental information can be used as input. In this presentation we will discuss recent and future measurements of relevant hadronic cross sections and transition form factors. [ABSTRACT FROM AUTHOR]

Studies of light pseudoscalar mesons are an important aspect of the physics program pursued at BESIII. In this presentation recent results from η and η' decays and the current status of the γγ physics program will be discussed. [ABSTRACT FROM AUTHOR]

The investigation of η' → ππη allows to study ππ and ηπ interactions and the possible influence of the scalar states f0(600) and a0(980) on the decay dynamics. 1.7 fb-1 of data taken with the KLOE detector at the DAΦNE e+e- collider have been analyzed with respect to the charged decay mode η' → π+π-η. 7900 ± 90 event candidates have been extracted and can be used for a Dalitz plot analysis. [ABSTRACT FROM AUTHOR]