Excitations in208Pb nearE x=5683 keV

A search for the recently proposed two-phonon octupole vibrational (2-POV) 4⁺ or 6⁺ state in²⁰⁸Pb at an excitation energy of 5683 keV has been performed using the²⁰⁷Pb(d,p),²⁰⁸Pb (p,p) and (,) reactions at high energy resolution. No evidence for a two-phonon excitation at this energy is found.This work was supported in part by the DFG under contract nr. II C4-Gr 894/2-1 and by the DFG-Graduiertenkolleg Struktur der Hadronen und Kerne under contract nr. Mu 705/3-1.     

Observation of the decaya 2 − (1320)→π − η′

The reaction ^– C ^– C has been studied at 36 GeV/c. A clear signal for the decaya ₂ ^– (1320) ^– · is observed in the ^– mass spectrum. The measured ratio of branchings is BR (a ₂ ^{– –} )/BR(a ₂ ^{– –} );(3.4±0.8±0.5)·10^–2.     

The decay of spin-isospin modes in a semi-infinite slab

The surface response for charge exchange (p, n) and (³He, T) reactions is studied in the-region using the semi-infinite slab model. The contribution to the total response from different decay channels, (NN, N, ), is calculated. These decay channels corresponds to the exclusive channels, (pp, p ⁺, ⁺), measured in recent (p, n) and (³He, T) experiments. The in-medium properties of the-resonance is taken into account by using microscopic calculations of the-width in nuclear matter. From the-width in nuclear matter a non-local imaginary-potential, as well as a local potential, is constructed for the semi-infinite slab model. The results in the semi-infinite slab model gives a qualitative understanding of the exclusive experiments. The exclusive (NN, N, ) channels are more sensitive, than the total response, tog-correlation parameters,-width and the absorption function used at the external vertex. Our calculations suggest low values of theg-correlation parametersg _N andg , (0.3). The results with the-width represented as a non-local or a local-potential are very similar, with only minor differences in the exclusive channels.Supported in part by the Swedish Natural Science Research Council and by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Nuclear Physics Division of the U.S. Department of Energy under Contract No. DE-ACO3-76SF00098     

The decays of theρ′1 andω′1 mesons

New measurements of the reactione ⁺ e ^– confirm previous evidence for the decay₁ and provide a strong constraint on the mass of the₁. The results from a detailed analysis of these data are compared with those from a corresponding analysis of new data on the reactione ⁺ e ^–. It is shown that in accord with expectation. This identification of a strong₁ decay supports a previous claim that the₁ and theC(1480), observed in the channel, cannot be different manifestations of the same particle.     

Ways to measure the hairpin diagram in charmed meson decays

The possible presence of hairpin diagrams is analyzed in th model-independent quark-diagram scheme for two-body decays of charmed mesons. Current experimental data do not require the presence of hairpin diagrams inDVP (V: vector meson,P: pseudoscalar meson), in accordance with the OZI rule. However, there is a possible indication that they are important in the decay ofDPP. The measurement ofD _s ^{+ +} is crucial to test the mechanism of hairpin diagrams.     

Search for the 70 keV resonance in17O(p, α)14N

A direct search for theE _R =70 keV resonance in¹⁷O(p, )¹⁴N was carried out using¹⁷O enriched Ta₂O₅ targets in combination with a 1 mA proton beam and suitable detectors of large solid angle. The observed upper limit for the resonance strength is8×10^–10 eV.Work supported in part by Deutsche Forschungsgemeinschaft (Ro429/21-2) and the Science Program SC1-0065 of the European Economic Community     

New bounds on the number of bound states for Schrödinger operators

We consider the Schrödinger operatorH = – +V(|x|) onR ³. Letn denote the number of bound states with angular momentum (not counting the 2 + 1 degeneracy). We prove the following bounds onn . LetV 0 and d/dr r ^1-2p (-V)^{1 –p} 0 for somep [1/2, 1) then

The\bar pp \to e^ + e^ - reaction at rest and the hierarchy of the annihilation ranges

A new procedure is devised to evaluate the proton form-factor at the ¯pp threshold from experimental data on ¯ppe ⁺ e ^– annihilation at rest. Comparison of the ¯ppe ⁺ e ^– and¯pp ^+– processes reveals that annihilation ranges for various channels are ranked in line with quark dynamics.This work has been funded in part by the German Federal Minister for Research and Technology (BMFT) under the contract number 06HD756     

Continued fractions and fermionic representations for characters of M(p,p′) minimal models

We present fermionic sum representations of the characters _{, s} ^{(p, p)} of the minimal M(p,p) models for all relatively prime integers p>p for some allowed values of r and s. Our starting point is biomial (q-binomial) identities derived from a truncation of the state counting equations of the XXZ spin 1/2 chain of anisotropy –=–cos((p/p)). We use the Takahashi-Suzuki method to express the allowed values of r (and s) in terms of the continued fraction decomposition of {p/p} (and p/p), where {x} stands for the fractional part of x. These values are, in fact, the dimensions of the Hermitian irreducible representations of SU _q- (2) (and SU _q+ (2)) with q–=exp(i{p/p}) (and q+=exp(i(p/p))). We also establish the duality relation M(p,p) M(p–p,p) and discuss the action of the Andrews-Bailey transformation in the space of minimal models. Many new identities of the Rogers-Ramanujan type are presented.Dedicated to Prof. Vladimir Rittenberg on his 60th birthday     

An upgraded analysis of ɛ′/ɛ at the next-to-leading order

An upgraded analysis of ,x _d and /, using the latest determinations of the relevant experimental and theoretical parameters, is presented. Using the recent determination of the top quark mass,m _t =(174±17) GeV, our best estimate is /=(3.1±2.5)×10^–, which lies in the range given by E731. We describe our detemination of / and make a comparison with other similar studies. A detailed discussion of the matching of the full theory to the effective Hamiltonian, written in terms of lattice operators, is also given.     

Photon-deuteron diffractive scattering

One expects a similarity of the energy dependence of the difference _tot(*p)– _tot(*n) for virtual (deep inelastic scatteringQ ²m ²) and real (Q ²=0) photons. Previous analysis of D structure functions with allowence for nuclear shadowing (NS) in the deuteron has led to conclusion that _tot(*p)– _tot(*n)<0>x<0.015. the=" early=" evidence=" from=" the=" real=" photoproduction=" data="> _tot(p)– _tot(n)<0. we=" critically=" reexamine=" determinations=" of=" the="> _tot(p)– _tot(n), using more accurate calculations of NS correction to _tot(D), and discuss a possibility of _tot(n) _tot(p) at moderately high energies.     

Vector two-point functions in maximally symmetric spaces

We obtain massive and massless vector two-point functions in maximally symmetric spaces (and vacua) of any number of dimensions. These include de Sitter space and anti-de Sitter space, and their Euclidean analogsS ⁿ andH ⁿ. Our method is based on a simple way of constructing every possible maximally symmetric bitensorT _a...bc...d(x, x) which carries tangent-space indicesa...b atx andc...d atx.     

Spin-current contributions to M2 excitations of 1p-shell nuclei

Microscopic analysis of spin-current contributions to magnetic quadrupole resonances in (e, e) cross sections has been performed using the particle-core coupling version of the shell model for 1p-shell nuclei. The contributions from spin-dipole and spin-octupole modes to M2 excitations of 1p-shell nuclei are traced up toq2.5 fm^–1.     

On the possibilities to study the exotic state 1−+ in photoproduction of the πη, πη′ systems

We show that photoproduction experiments provide propitious conditions to study the exotic state 1^–+ in the and channels. For unpolarized photons contributions from natural and unnatural parity exchanges do not interfere with each other, a fact which permits to estimate the correctness of phase shift analyses. In photoproduction of the ⁺ system in the mass range ofa ₂(1320) a more stringent limit on the product (1^–+)Br(1^–+) can be obtained than in experiments on Primakoff production on nuclei. Particularly favourable is the study of the state 1^–+ in the coherent photoproduction of the ⁰ and ⁰ systems on nuclei, with significantly enlarged statistics and a simplified phase shift analysis.     

K→ππγ decays: A search for novel couplings in kaon decays

We analyzeK decays in the framework of Chiral Perturbation Theory. We study the different Dalitz plot distributions, trying to find regions whereo(p ⁶) contributions could be more easily detected. To fulfill this program we compute all theo(p ⁴) loop and counterterm contributions, finding a substantial agreement with the existing calculations and adding some small missing terms inK _S ^+–.Work supported in part by the Human Capital and Mobility Program, EEC Contract N. CHRX-CT920026     

Masses of colored vector mesons

Mass formulas for colored vector mesons are derived under the assumption of one common mixing angle forSU(3), independent of the color quantum numbers, and correspondingly one common mixing angle () forSU(3). This a priori plausible assumption turns out to have strong implications and thus might be too restrictive. We allow for a non-trivial spatial overlap integral between color-singlet and color-octet states. Various cases are treated and physical possibilities are identified. The best agreement is obtained for = 0. There are two models of this type with and without a part of the symmetry breaking Hamiltonian density transforming as (Y, Y) underSU(3)SU(3). Models with 0 are also possible. They cannot have a (Y, Y) and predict 3.34 GeV as the mass of the (3.7). This error of 10% may however be used to reject this possibility. Masses of colored vector mesons are predicted in the various models. If a (Y, Y) is present, ideal mixing inSU (3) is implied by the general formalism of the model.     

Testing the Higgs system at a photon-photon collider

The level of sensitivity of the processes ZZ, W ⁺ W ^– and to the Higgs sector of the Standard Model Lagrangian in the energy region between 200 GeV and 1 TeV is examined. The elementary Higgs boson is taken to have a mass less than 1 TeV. Sizeable effects are found in theZZ and channels if the incoming photons have the same helicity. Also the possibility that the elementary Higgs boson does not exist is examined. Assuming new physics to show up in the TeV energy region the cross sections are evaluated according to the heavy Higgs model. For center of mass energy values close to 1 TeV interesting effects are found in the channel if the photons have the same helicity. The limit of large Higgs mass is not unique. The parametrization of this arbitrariness may be interpreted as a representation of the new physics. The effects for the processes ZZ and are investigated. These effects may be correlated to a possible resonance inWW scattering in the TeV region.     

Contributions toΛ c + →πΣ,πΛ andp\bar K^0 from excited states

We consider contributions to _c ⁺ , and from excited states. The calculations are performed within the MIT-bag model and a heavy quark bag model. Because the mass of _c ⁺ is rather big compared to the strange baryons, excited baryon states with mass close to that of _c ⁺ in some cases give significant pole contributions to the decay amplitudes of _c ⁺ .     

Studies of the reactionπ − p→η ′ π 0 n at 38 and 100 GeV/c

The production of ⁰ system in ^– _p charge-exchange interactions at ^– momenta 38 GeV/c and 100 GeV/c has been studied. The 2 and ^{0 0} decay modes of leading to 4 and 8 final states respectively have been detected. No statistically significant peak is observed in the ⁰ mass spectrum in the range of 1.2 GeV÷2.1 GeV. An upper limit of 6·10^–3 has been established for thea ₂ ⁰ (1320) ⁰ branching ratio.