Uri Maor
The role of data analysis in the formation of recent unitarity models is discused and evaluated. It is claimed that present support for multi Pomeron enhancement beyond the zero order is marginal and should be checked at LHC and Auger.
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We update and summarize the present status of our understanding of the reparametrization symmetry with $i \leftrightarrow j$ state exchange in neutrino oscillation in matter. We introduce a systematic method called ``Symmetry Finder'' (SF) to uncover such symmetries, demonstrate its efficient hunting capability, and examine their characteristic features. Apparently they have a local nature: The 1-2 and 1-3 state exchange symmetries exist at around the solar- and atmospheric-resonances, respectively, with the level-crossing states exchanged. However, this view is not supported, to date, in the …
Multiple interaction models satisfying $s$-channel unitarity predict that, in contrast to inelastic processes, factorization is violated in diffractive processes. The size of this effect can be characterized in terms of the rapidity gap survival probability. The possibility of its measurement at HERA is pointed out. Furthermore a method to measure photon diffraction dissociation at LEP2 and planned linear colliders is discussed and cross section predictions are given.
Recently, a more than 2sigma discrepancy has been observed between the well measured inclusive value of Vub and the predicted value of Vub from the unitarity triangle fit using the world average value of sin2beta. We attempt to resolve this tension in the context of grand unified SO(10) and SU(5) models where the neutrino mixing matrix is responsible for flavor changing neutral current at the weak scale and the models with non-proportional A-terms (can be realized simply in the context of intersecting D-brane models) and investigate the interplay between the constraints arising from B_{s,d}-\b…
The relation between scattering and production amplitudes imposed by unitarity and analyticity, recently criticised by Ishida et al., is explained.
We review on the recent developments for the computation of scattering amplitudes, with attention to the on-shell formalisms and unitarity-based methods.
We study UV complete theories where the Standard Model (SM) gauge group is extended with a new abelian $U(1)$, and the field content is augmented by an arbitrary number of scalar and fermion SM singlets, potentially including dark matter (DM) candidates. Considerations such as classical and quantum gauge invariance of the full theory and S-matrix unitarity, not applicable within a simplified model approach, are shown to have significant phenomenological consequences. The lack of gauge anomalies leads to compact relations among the $U(1)$ fermion charges, and puts a lower bound on the number of…
We explore the unitarity violation of the CKM matrix in the model in which the third generation fermions are subjected to the separate SU(2)$_L$ gauge interaction. With the recent LEP and SLC data at $Z$-pole and low-energy neutral current interaction data, the analysis on the parameter space of the model is updated, and the unitary violation is predicted under the constraint.
Prompted by the recent observation of a Higgs-like particle at the CERN Large Hadron Collider (LHC), we investigate a quantitative correlation between possible departures of the gauge and Yukawa couplings of this particle from their Standard Model expectations and the scale of unitarity violation in the processes $WW \to WW$ and $t\bar t \to WW$.
In the light of the recent LHC data, we study precision tests sensitive to the violation of lepton universality, in particular the violation of unitarity in neutrino mixing. Keeping all data we find no satisfatory fit, even allowing for violations of unitarity in neutrino mixing. Leaving out sin$^2 θ_{\scriptsize \mbox{eff}}$ from the hadronic forward-backward asymmetry at LEP, we find a good fit to the data with some evidence of lepton universality violation at the $\mathcal{O}(10^{-3})$ level.
By using the most recent determinations of the several theoretical and experimental input parameters, we update the Unitarity Triangle analysis in the Standard Model and discuss the sensitivity to New Physics effects. We investigate the interest of measuring with a better precision the various physical quantities entering the Unitarity Triangle analysis and study in a model independent way whether, despite the undoubted success of the CKM mechanism in the Standard Model, the Unitarity Triangle analysis still allows the presence of New Physics.
We discuss new techniques developed in recent years for performing one-loop calculations in QCD, and present an example of results from the process 0 -> V q q-bar g g. Talk presented at the 1996 Zeuthen Workshop on Elementary Particle Theory, "QCD and QED in Higher Order", Rheinsberg, Brandenburg, April 21-26, 1996.
We summarize recent work on the characterization of anomaly poles in connection with the field-theory interpretation of the Green-Schwarz mechanism of anomaly cancellation and on their effective field theories, stressing on the properties of the anomaly vertex in two representations, the Rosenberg and the Longitudinal/Transverse. The presence of polar amplitudes in these theories causes a violation of unitarity at high energy which is cured by the exchange of the axion. We comment on the possible physical implications of this mechanism.
We perform a combined analysis of the unitarity triangle and of the CP violating parameter epsilon'/epsilon using the most recent determination of the relevant experimental data and, whenever possible, hadronic matrix elements from lattice QCD. We discuss the role of the main non-perturbative parameters and make a comparison with other recent analyses. We use lattice results for the matrix element of Q_8 obtained without reference to the strange quark mass. Since a reliable lattice determination of the matrix element of Q_6 is still missing, the theoretical predictions for epsilon'/epsilon suf…
A review is given of recent developments in the physics of flavor. Current constraints on the Cabibbo-Kobayashi-Maskawa matrix are discussed and related to the recent measurements of epsilon'/epsilon, sin(2beta) and K+ -> pi+ nu nubar. A brief review is given of the connection between CP violation in B decays and electroweak baryogenesis. Finally, there is an extensive discussion of how present and proposed experiments in K and B physics can constrain the pattern of flavor changing processes at low energies and, one hopes, eventually provide unambiguous evidence of physics beyond the Standard …
We use the recently measured accurate BaBaR data on the modulus of the pion electromagnetic form factor, $F_π(t)$, up to an energy of 3 GeV, the I=1 $P$-wave phase of the $ππ$ scattering amplitude up to the $ω-π$ threshold, the pion charge radius known from Chiral Perturbation Theory, and the recently measured JLAB value of $F_π$ in the spacelike region at $t=-2.45 {\rm GeV}^2$ as inputs in a formalism that leads to bounds on $F_π$ in the intermediate spacelike region. We compare our constraints with experimental data and with perturbative QCD along with the results of several theoretical mode…
The trace anomaly in external gravity is the sum of three terms at criticality: the square of the Weyl tensor, the Euler density and Box R, with coefficients, properly normalized, called c, a and a', the latter being ambiguously defined by an additive constant. Considerations about unitarity and positivity properties of the induced actions allow us to show that the total RG flows of a and a' are equal and therefore the a'-ambiguity can be consistently removed through the identification a'=a. The picture that emerges clarifies several long-standing issues. The interplay between unitarity and re…
We present results of a combined analysis in neutrino oscillations without unitarity assumption in the $3ν$ mixing picture. Constraints on neutrino mixing matrix elements are based on recent data from the reactor, solar and long-baseline accelerator neutrino oscillation experiments. The current data are consistent with the standard $3ν$ scheme. The precision on different matrix elements can be as good as a few percent at $3σ$ CL, and is mainly limited by the experimental statistical uncertainty. The $ν_e$ related elements are the most precisely measured among all sectors with the uncertainties…
We present a detailed numerical study of the K_{e3} decays to O(p^6,(m_d-m_u)p^2,e^2p^2) in chiral perturbation theory with virtual photons and leptons. We describe the extraction of the CKM matrix element |V_{us}| from the experimental K_{e3} decay parameters. We propose a consistency check of the K^+_{e3} and K^0_{e3} data that is largely insensitive to the dominating theoretical uncertainties, in particular the contributions of order p^6. Our analysis is highly relevant in view of the recent high statistics measurement of the K^+_{e3} branching ratio by E865 at Brookhaven which does not ind…
Lattice QCD has always played a relevant role in the studies of flavor physics and, in particular, in the Unitarity Triangle (UT) analysis. Before the starting of the B factories, this analysis relied on the results of lattice QCD simulations to relate the experimental determinations of semileptonic B decays, K-Kbar and B_{d,s}-B_{d,s}bar mixing to the CKM parameters. In the last years much more information has been obtained from the direct determination of the UT angles from non-leptonic B decays. In this talk, after a presentation of recent averages of lattice QCD results, we compare the out…
We study the linking between the CP violating phase of the lepton sectors and the unitarity triangle of the B0 meson system. Antusch, King, Malinsky and Spinrath have shown that the quark mass matrices with the negligible 1-3 mixing give an interesting relation between the phase of the quark mixing matrices and CP violating measure phi_2(alpha). This approach is extended by considering the SO(10) GUT including the Pati-Salam symmetry, which links the Yukawa matrices of the quark sector to the one of the lepton sector. We discuss the relation of the CP violating phases between both quark and le…
Analysis of the $ψ(3770)$ resonance in line with unitarity and analyticity constraints
本文用满足幺正性与解析性的耦合道 K 矩阵方法拟合3.70–3.83 GeV强子产生数据，测定 $ψ(3770)$ 参数并约束其非 $D\bar D$ 衰变。
We review recent results of Lattice QCD calculations relevant for flavour physics. We discuss in particular the hadronic parameters entering the amplitudes of K0-K0bar, D0-D0bar and B0-B0bar mixing, the B- and D-meson decay constants and the form factors controlling B-meson semileptonic decays. On the basis of these lattice results, which are extensively collected in the paper, we also derive our averages of the relevant hadronic parameters.
The recent discovery of a 126 GeV boson at the LHC will be followed by a detailed examination of its couplings in order to determine whether this particle is the Higgs boson of the standard model or one of many particles of an extended scalar sector. One such extension with a rich phenomenology consists of a color octet electroweak doublet scalar. The most general renormalizable scalar potential contains twelve new parameters and it is therefore desirable to constrain them. We present theoretical constraints on these parameters obtained by requiring perturbative unitarity for two-to-two scalar…
The nature of the X(3872) enhancement is analysed in the framework of the Resonance-Spectrum Expansion, by studying it as a regular $J^{PC}=1^{++}$ charmonium state, though strongly influenced and shifted by open-charm decay channels. The observed but Okubo-Zweig-Iizuka-forbidden $ρ^0 J/ψ$ and $ωJ/ψ$ channels are coupled as well, but effectively smeared out by using complex $ρ^0$ and $ω$ masses, in order to account for their physical widths, followed by a rigorous algebraic procedure to restore unitarity. A very delicate interplay between the $D^0 D^{*0}$, $ρ^0 J/ψ$, and $ωJ/ψ$ channels is obs…
Motivated by the discrepancies noted recently between the theoretical calculations of the electromagnetic $ωπ$ form factor and certain experimental data, we investigate this form factor using analyticity and unitarity in a framework known as the method of unitarity bounds.We use a QCD correlator computed on the spacelike axis by operator product expansion and perturbative QCD as input, and exploit unitarity and the positivity of its spectral function, including the two-pion contribution that can be reliably calculated using high-precision data on the pion form factor. From this information, we…
We propose a practical parametrisation for the line shapes of near-threshold states compatible with all requirements of unitarity and analyticity. The coupled-channel system underlying the proposed parametrisation includes bare poles and an arbitrary number of elastic and inelastic channels treated fully nonperturbatively. The resulting formulae are general enough to be used for a simultaneous analysis of the data in all available production and decay channels of the (system of) state(s) under consideration for a quite wide class of reactions. As an example, we fit the experimental data curren…
The two-pion contribution from low energies to the muon magnetic moment anomaly, although small, has a large relative uncertainty since in this region the experimental data on the cross sections are neither sufficient nor precise enough. It is therefore of interest to see whether the precision can be improved by means of additional theoretical information on the pion electromagnetic form factor, which controls the leading order contribution. In the present paper we address this problem by exploiting analyticity and unitarity of the form factor in a parametrization-free approach that uses the p…
The importance of $S$-matrix unitarity in realistic meson spectroscopy is reviewed, both its historical development and more recent applications. First the effects of imposing $S$-matrix unitarity on meson resonances is demonstrated in both the elastic and the inelastic case. Then, the static quark model is revisited and its theoretical as well as phenomenological shortcomings are highlighted. A detailed account is presented of the mesons in the tables of the Particle Data Group that cannot be explained at all or only poorly in models describing mesons as pure quark-antiquark bound states. Nex…
We have analysed pion photoproduction imposing constraints from fixed t dispersion relations and unitarity. Coupled integral equations for the S and P wave multipoles were derived from the dispersion relations and solved by the method of Omnes and Muskhelishvili. The free parameters were determined by a fit to the most recent data for π^{+} and π^{0} production on the proton as well as π^{-} production on the neutron, in the energy We have analysed pion photoproduction imposing constraints from fixed t dispersion relations and unitarity. Coupled integral equations for the S and P wave multipol…
Unitarity violation and restoration in radiative bound-state formation
针对暗物质的前沿计算显示，辐射束缚态形成过程中非相对论区域的分波幺正性严重破坏，通过适当重求和入射态自能中的非弹性贡献可恢复幺正性，本文推导了分波的Kramers型公式并分析了复动量平面上的解析结构。
High-statistics data on the $e^+e^-\to π^+π^-$ cross section and the pion vector form factor have been obtained recently by several collaborations. Unfortunately, there are some tensions between different datasets, especially the most precise ones, which have not been resolved so far. Additional independent constraints on the data are therefore of interest. We consider a parametrization-free method of analytic extrapolation proposed recently, which is based on a mixed phase and modulus extremal problem and combines rigorous upper and lower bounds with numerical simulations to account for the s…
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