Search for the Rare Decays K L → π 0 π 0 μ + μ − and K L → π 0 π 0 X 0 → π 0 π 0 μ + μ −
Not Available
Abouzaid, E.↗
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Chiral Effective Field Theory Predictions for Muon Capture on Deuteron and 3 He
Not Available
Marcucci, L. E.↗
Quark matter and meson properties in a Nonlocal SU(3) chiral quark model at finite temperature
We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with a background color field. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles, and decay constants.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Analysis of the QCD spectrum and chiral symmetry breaking with varying quark masses
The meson spectrum of QCD is studied in the framework of nonperturbative QCD as a function of varying quark masses m{sub q}. It is shown that the total spectrum consists of two branches: 1) the standard one, which may be called the flux-tube spectrum, depending approximately linearly on m{sub q}, and 2) the chiral symmetry breaking (CSB) spectrum for pseudoscalar (PS) flavor nonsinglet mesons with mass dependence {radical}m{sub q}. The formalism for PS mesons is derived from the QCD Lagrangian with m{sub q} corrections, and a unified form of the PS propagator was derived. It is shown that the CSB branch of PS mesons joins to the flux-tube branch at around m{sub q} = 200 MeV. All these results are in close correspondence with recent numerical data on large lattices.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
On the ππ-scattering lengths in the theory with effective Lagrangian
Use of the effective Lagrangian incorporating both the scalar and pseudoscalar mesons gives a possibility to calculate the ππ-scattering lengths without attraction of the ChPT theory.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
On the extraction of cross sections for π{sup 0} and η photoproduction off neutrons from deuteron data
We discuss the procedure of extracting the photoproduction cross section for neutral pseudoscalar mesons off neutrons from deuteron data. The main statement is that the final-state-interaction corrections for the proton and neutron target are in general not equal, but for π{sup 0} production there are special cases where they have to be identical and there are large regions in the parameter space of incident photon energy and pion polar angle, Θ*, where they happen to be quite similar. The corrections for both target nucleons are practically identical for π0 production in the energy range of the Δ(1232)3/2+ resonance due to the specific isospin structure of this excitation. Also above the Δ-isobar range large differences between proton and neutron correction factors are only predicted for extreme forward angles (Θ* *lt; 20°), but the results are similar for larger angles. The case of η photoproduction is also briefly considered. Numerical results for the γp → π{sup 0}p and γn → π{sup 0}n correction factors are discussed. Also the model description for the available data on the differential γd → π{sup 0}pn cross sections are given.
74 ATOMIC AND MOLECULAR PHYSICS↗
Lepton decay constants of light mesons
A theory of lepton decay constants based on the path-integral formalism is given for chiral and vector mesons. Decay constants of the pseudoscalar and vector mesons are calculated and compared to other existing results.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Wave functions and mass spectrum for a system of two relativistic spinor quarks coupled by a chromodynamical interaction
Exact solutions of relativistic quasipotential equations in the configuration representation were found for a system of two spin-1/2 quarks interacting via a Coulomb-like chromodynamical potential. Quantization conditions were found for the pseudoscalar, pseudovector, and vector cases. The present analysis was performed within the Hamiltonian formulation of quantum field theory via a transition to the relativistic configuration representation for the case of two relativistic spin-1/2 quarks of equal mass.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Relationship between T-invariance and formation mechanisms for T-odd and T-even asymmetries in the angular distributions of fission fragments of oriented nuclei
The T-invariance condition was analyzed for the amplitude T{sub b,a} of multiparticle multistep elastic or inelastic a → b nuclear reactions. This condition leads to the equality of the amplitude T{sub b,a} to the amplitude T̃{sub ā,b̄} of b̄→ā time-reversed reaction, for which the reaction operator T̃ coincides with the inverse-reaction (b → a) operator. It is shown that, in the case where the original, inverse, and time-reversed reactions are governed by a common T-invariant mechanism, the coefficients D of asymmetries appearing in the differential cross sections for these reactions can be represented in the form of a unified scalar (pseudoscalar) function of arguments equal to the momentum and spin vectors of particles of the initial and final channels of the reactions under analysis. It is also shown that the use of the T-invariance condition for the coefficients D of asymmetries in the differential cross section for the original nuclear reaction that are different in P- and T-parity makes it possible to separate mechanisms leading to nonzero coefficients D for a number of the asymmetries under analysis from the remaining mechanisms leading to zero coefficients D of these asymmetries. It is proven that there exist such asymmetries in the differential cross section for the original reaction whose coefficients vanish for all possible T-invariant mechanisms of their appearance, so that, upon proving experimentally the appearance of nonzero coefficients of these asymmetries in the differential cross section for the original reaction, this fact can be used to assess features of T-noninvariant interactions in nuclear systems.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Application of T-Invariance Conditions in Selecting Mechanisms of Nuclear Reactions, Decays, and Fission
T-invariance conditions for the differential cross sections of multiparticle multistep nuclear reactions are found with allowance for spin orientations of particles in the initial channels of such reactions. It is shown that the asymmetry coefficients for different T-parities in the differential cross sections for original and time-reversed reactions are expressed in terms of unified scalar (pseudoscalar) functions that depend of the 3-momenta and spins of particles involved in the initial and final channels of the reactions under analysis. It is also shown that knowledge of the aforementioned functions for the asymmetries under analysis in the original reaction makes it possible to reconstruct the respective functions for the analogous asymmetries in the time-reversed reaction without studying it experimentally. By considering the example of T-even and T-odd asymmetries in reactions where oriented nuclei undergo binary and ternary fission induced by cold polarized neutrons, it is demonstrated that the T-invariance conditions in question can be used to select mechanisms behind the appearance of the above asymmetries—in particular, mechanisms associated with the presence of T-noninvariant interactions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Polarized and transversity GPDs in kaon leptoproduction
We study the kaon leptoproduction on the basis of the handbag approach. We consider the leading-twist contribution together with the transversity twist-3 effects which were found to be important in the description of pseudoscalar meson production. We present our predictions for the cross section and spin asymmetries in the kaon leptoproduction.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Selected Topics on Hadronic B Decays From BaBar
Recent measurements of branching fractions and decay-rate asymmetries in charmless hadronic B decays at the BaBar experiment are presented. The selected topics include Dalitz plot analyses of B {yields} K{sup +} {pi}{sup -}{pi} and signal searches in B {yields} PP and PV, where isoscalar mesons are involved, and in B {yields} b{sub 1}P, P and V denote a pseudoscalar and vector meson, respectively. Several measurements in charmless hadronic B decays have indicated possible deviations from the theoretical predictions within the Standard Model. The measurements presented would contribute to searching for and resolving such puzzles.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Search for 14.4-KeV Solar Axions Emitted in the M1-Transition of Fe-57 Nuclei with CAST
We have searched for 14.4 keV solar axions or more general axion-like particles (ALPs), that may be emitted in the M1 nuclear transition of 57Fe, by using the axion-to-photon conversion in the CERN Axion Solar Telescope (CAST) with evacuated magnet bores (Phase I). From the absence of excess of the monoenergetic X-rays when the magnet was pointing to the Sun, we set model-independent constraints on the coupling constants of pseudoscalar particles that couple to two photons and to a nucleon g{sub ay}|-1.19g{sub aN}{sup 0}+g{sub aN}{sup 3}| < 1.36 x 10{sup -16} GeV{sup -1} for ma < 0.03 eV at the 95% confidence level.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Lepton Universality Test in Upsilon(1S) Decays at BaBar
Using a sample of 122 million {Upsilon}(3S) decays collected with the BABAR detector at the PEP-II asymmetric energy collider at the SLAC National Accelerator Laboratory, we measure the ratio R{sub {tau}{mu}} = BR({Upsilon}(1S) {yields} {tau}{sup +}{tau}{sup -})/BR({Upsilon}(1S) {yields} {mu}{sup +}{mu}{sup -}); the measurement is intended as a test of lepton universality and as a possible search for a light pseudoscalar Higgs boson in Next to Minimal Supersymmetric Standard Model (NMSSM) scenarios. Such a boson could appear in a deviation of the ratio R{sub {tau}{mu}} from the Standard Model expectation, that is 1, except for small lepton mass corrections. The analysis exploits the decays {Upsilon}(3S) {yields} {Upsilon}(1S){pi}{sup +}{pi}{sup -}, {Upsilon}(1S) {yields} l{sup +}l{sup -}, where l = {mu},{tau}.
43 PARTICLE ACCELERATORS↗
Hadron Spectroscopy Program with CLAS g12
Some conclusions from this presentation are: (1) previous CLAS result on exotic {pi}{sub 1}(1600)/{alpha}{sub 2}(1320) in photoproduction confirmed with higher statistics; (2) previous CLAS result on {gamma}p {yields} pentaquark not confirmed with higher statistics; (3) high luminosity allows exploitation of rare topologies {gamma}p {yields} {phi}{pi}{sup 0}p, {phi}{eta}p, {phi}{omega}p; (4) no observation of any {Xi}* states above 1530 MeV recoiling off of K{sup +}K{sup +} lepton detection permits high statistic study of pseudoscalar dalitz decay; and (5) first observation of {eta}' Dalitz decay, {rho}-{omega} interference via e{sup +}e{sup -} channel.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Intrinsic transverse momentum and parton correlations from dynamical chiral symmetry breaking
The dynamical breaking of chiral symmetry in QCD is caused by nonperturbative interactions on a distance scale rho ~ 0.3 fm, much smaller than the typical hadronic size R ~ 1 fm. These short-distance interactions influence the intrinsic transverse momentum distributions of partons and their correlations at a low normalization point. We study this phenomenon in an effective description of the low-energy dynamics in terms of chiral constituent quark degrees of freedom, which refers to the large-N_c limit of QCD. The nucleon is obtained as a system of constituent quarks and antiquarks moving in a self-consistent classical chiral field (relativistic mean-field approximation, or chiral quark-soliton model). The calculated transverse momentum distributions of constituent quarks and antiquarks are matched with QCD quarks, antiquarks and gluons at the chiral symmetry--breaking scale rho^{-2}. We find that the transverse momentum distribution of valence quarks is localized at p_T^2 ~ R^{-2} and roughly of Gaussian shape. The distribution of unpolarized sea quarks exhibits a would-be power-like tail ~1/p_T^2 extending up to the chiral symmetry-breaking scale. Similar behavior is observed in the flavor-nonsinglet polarized sea. The high-momentum tails are the result of short-range correlations between sea quarks in the nucleon's light-cone wave function, which are analogous to short-range NN correlations in nuclei. We show that the nucleon's light-cone wave function contains correlated pairs of transverse size rho << R with scalar-isoscalar (Sigma) and pseudoscalar-isovector (Pi) quantum numbers, whose internal wave functions have a distinctive spin structure and become identical at p_T^2 ~ rho^{-2} (restoration of chiral symmetry). These features are model-independent and represent an effect of dynamical chiral symmetry breaking on the nucleon's partonic structure. Our results have numerous implications for the transverse momentum distributions of particles produced in hard scattering processes. Under certain conditions the nonperturbative parton correlations predicted here could be observed in particle correlations between the current and target fragmentation regions of deep-inelastic scattering.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
The photo-philic QCD axion
Here, we propose a framework in which the QCD axion has an exponentially large coupling to photons, relying on the “clockwork” mechanism. We discuss the impact of present and future axion experiments on the parameter space of the model. In addition to the axion, the model predicts a large number of pseudoscalars which can be light and observable at the LHC. In the most favorable scenario, axion Dark Matter will give a signal in multiple axion detection experiments and the pseudo-scalars will be discovered at the LHC, allowing us to determine most of the parameters of the model.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Lattice operators for scattering of particles with spin
We construct operators for simulating the scattering of two hadrons with spin on the lattice. Three methods are shown to give the consistent operators for P N, P V, V N and N N scattering, where P, V and N denote pseudoscalar, vector and nucleon. Explicit expressions for operators are given for all irreducible representations at lowest two relative momenta. Each hadron has a good helicity in the first method. The hadrons are in a certain partial wave L with total spin S in the second method. These enable the physics interpretations of the operators obtained from the general projection method. The correct transformation properties of the operators in all three methods are proven. Lastly, the total momentum of two hadrons is restricted to zero since parity is a good quantum number in this case.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗