A study of the nuclear-medium influence on neutral-strange-particle production in deep-inelastic neutrino scattering

The influence of nuclear effects on the production of neutral strange particles (V ⁰) is investigated using the data obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E _v =3−30 GeV) at the Serpukhov accelerator. The mean multiplicity of V ⁰ particles in nuclear interactions, , is found to exceed significantly that in “quasideuteron” interactions, . The ratio of is larger than that for π⁻ mesons, . It is shown that the multiplicity gain of V ⁰ particles can be explained by intranuclear interactions of produced pions. The text was submitted by the authors in English.     

Quark-gluonium content of the scalar-isoscalar states f0(980), f0(1300), f0(1500), f0(1750), and f0(1420 ?70+150 ) from hadronic decays

On the basis of the decay couplings f ₀ → ππ, K , ηη, ηη′ found earlier in the study of analytical (IJ ^PC =00⁺⁺) amplitude in the mass range 450–1900 MeV, we analyze the quark-gluonium content of the resonances f ₀(980), f ₀(1300), f ₀(1500), and f ₀(1750) and the broad state f ₀(1420 ₋₇₀ ⁺¹⁵⁰ ). The K-matrix technique used in the analysis makes it possible to evaluate the quark-gluonium content both for the states with switched-off decay channels (bare states, f ₀ ^bare ) and for the real resonances. We observe a significant change in the quark-gluonium composition in the evolution from bare states to real resonances, which is due to the mixing of states in the transitions f ₀(m ₁) → real mesons → f ₀ (m ₂) responsible for the decay processes as well. For f ₀(980), the analysis confirmed the dominance of q component, thus proving the n /s composition found in the study of the radiative decays. For the mesons f ₀(1300), f ₀(1500), and f ₀(1750), the hadronic decays do not allow one to determine uniquely the n , s , and gluonium components, providing relative percentage only. The analysis shows that the broad state f ₀(1420 ₋₇₀ ⁺¹⁵⁰ ) can mix with the flavor singlet q component only, which is consistent with gluonium origin of the broad resonance. From Yadernaya Fizika, Vol. 66, No. 4, 2003, pp. 772–785. Original English Text Copyright ? 2003 by Anisovich, Nikonov, Sarantsev. This article was submitted by the authors in English.     

Using the e ± μ? + E Tmiss signature in the search for supersymmetry and lepton-flavor violation in neutralino decays

The LHC (CMS) discovery potential in the search for supersymmetry and lepton-flavor violation in neutralino decays using the e ^± μ^∓ + E _T ^miss signature is studied. A detailed study is done for the CMS test points LM1-LM9. It is shown that, for the point LM1, it is possible to detect lepton-flavor violation in neutralino decays with lepton-flavor-violating branching Br( → μ^± e ^∓ ) ≥ 0.04 Br( → e ⁺ e ⁻ , μ⁺ μ⁻ ) for an integral luminosity of 10 fb⁻¹. The discovery potential in the mSUGRA-SUSY scenario with tan β = 10, sgn(μ) = + in the (m ₀, m _1/2) plane using the e ^± μ^∓ + E _T ^miss signature is determined. The text was submitted by the authors in English.     

CP -violation effects in the decays B ? → D * K *? and method for determining the weak phase γ

A method for determining the angle γ and the ratio of the amplitudes A _λ(B ⁻ → K ^*−) and A _λ)B ⁻ → D ^*0 K ^*−), r _Bλ, for all three vector-meson polarization states by using the decays B ^∓ → D ^* K ^*∓ is proposed. This method relies on the interference between the decays B ⁻ → D ^*0 K ^*− and B ⁻ → K ^*−, which arises if D ^*0 and decay to D ⁰/ π ⁰ and D ⁰/ γ, whereupon D ⁰ and mesons decay to common final hadron states. The doubly Cabibbo-suppressed modes of D ⁰-meson decay are chosen here to specify such final states. Original Russian Text ? V.A. Kovalchuk, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 4, pp. 754–763.     

Effective Lagrangians and IG(JPC)=1?(1?+) exotic resonance state in the VP and the PP channel

For I ^G (J ^PC)=1⁻(1⁻⁺) exotic waves in the reactions ρπ → ρπ, ρπ → ηπ, ρπ → η′π, and ρπ → and in allied reactions, a model is constructed that satisfies the conditions of unitarity and analyticity and which employs, as an input, an “anomalous” nondiagonal VPPP interaction relating the ρπ, ηπ, η′π, and channels. The possibility of obtaining, within this simple field-theoretical model, a resonance behavior of the I ^G(J ^PC)=1⁻(1⁻⁺) amplitudes corresponding to the {10} − and {8} representations of the SU(3) group and their mixing is demonstrated explicitly in the mass range 1.3–1.6 GeV, where data of present-day experiments suggest a rich exoticism. __________ Translated from Yadernaya Fizika, Vol. 65, No. 3, 2002, pp. 579–588. Original Russian Text Copyright ? 2002 by Achasov, Shestakov.     

On the LHC observation of gluinos from the Egret-preferred region

Prospects for observation of a SUSY-like signal from two gluinos are investigated within a certain region of the mSUGRA parameter space, where the cross section of the two-gluino production in pp-collisions at the LHC ( = 14 TeV) is estimated at a rather high level of 17.3 pb. In this so-called EGRET-preferred region, the lightest stable neutralinos χ ₁⁰ can serve as cold-dark-matter particles and can naturally explain the excess of diffuse Galactic gamma rays observed by the EGRET space apparatus. The -event selection relies on a clear signature when decay products of each gluino contain one b pair, one or two l pair(s) or one or two light q pair(s), and a neutralino. Rather high transverse missing energy carried away by the two neutralinos is the essential signature of the events using of which allows the relevant Standard Model background to be reduced significantly. Furthermore, distributions of the reconstructed invariant masses of two opposite-charged-lepton or light-jet pairs produced by the χ ₂⁰ → χ ₁⁰ l ⁺ l ⁻ and χ ₂⁰ → χ ₁⁰ q three-body decays have kinematic end points which measure the difference between masses of χ ₂⁰ and χ ₁⁰. In particular, it was found that these signatures of selected processes demonstrate good prospects for discovery of gluinos at the LHC. These signatures allow one to distinguish different mSUGRA parameters m _1/2 within the EGRET-preferred region (at a higher than 6σ confidence level with 300 fb⁻¹ data). The text was submitted by the authors in English.     

The <Emphasis Type="Italic">A</Emphasis> dependence of <Emphasis Type="Italic">K</Emphasis><Superscript>0</Superscript> and Λ Neutrinoproduction on nuclei

The A dependence of the production of K ⁰ and Λ is investigated for the first time in neutrino-nuclear reactions using the data obtained with the SKAT bubble chamber. An exponential parametrization (∼A ^β) of the particle yields results in = 0.20 ± 0.05 for V ⁰ particles (K ⁰ and Λ), while for π ⁻ mesons the A dependence is much weaker ( = 0.068 ± 0.007). A nuclear enhancement of the ratio K ⁰/π ⁻ is found; this ratio increases from 0.055 ± 0.013 for vN interactions up to 0.070 ± 0.011 at A ≈ 21 and 0.099 ± 0.011 at A ≈ 45. It is observed that the multiplicity rise of V ⁰ occurs predominantly in the backward hemisphere of the hadronic system. It is shown that the A dependence of the Λ⁰ and π ⁻ yields can be reproduced in the framework of a model incorporating the secondary intranuclear interactions of pions originating from the primary vN interactions. The text was submitted by the authors in English.     

Near-threshold production of a0(980) mesons in πN and NN collisions and a0-f0 mixing

We consider near-threshold a ₀(980)-meson production in πN and NN collisions. An effective Lagrangian approach with one-pion exchange is applied to analyze different contributions to the cross section for different isospin channels. The Reggeon exchange mechanism is also evaluated for comparison. The results from πN reactions are used to calculate the contribution of the a ₀ meson to the cross sections and invariant mass distributions of the reactions and pp → ppK ⁺ K ⁻. It is found that the experimental observation of a ₀ ⁺ mesons in the reaction is much more promising than the observation of a ₀ ⁰ mesons in the reaction pp → ppK ⁺ K ⁻. Effects of isospin violation in the reactions pN → da ₀, pd → ³He(³H)a ₀, and dd → ⁴Hea ₀, which are induced by a ₀(980)-f ₀(980) mixing, are also analyzed. From Yadernaya Fizika, Vol. 66, No. 1, 2003, pp. 155–174. Original English Text Copyright ? 2003 by Kondratyuk, Bratkovskaya, Grishina, Büscher, Cassing, Str?her. This article was submitted by the authors in English.     

a 0 + (980)-resonance production in the reaction pp → dπ + η close to the K\bar K threshold

The reaction pp → dπ ⁺ η has been measured at a beam energy of T _p = 2.65 GeV (p _p = 3.46 GeV/c) using the ANKE spectrometer at COSY-Julich. The missing-mass distribution of the detected dπ ⁺ pairs exhibits a peak around the η mass on top of a strong background of multipion pp → dπ ⁺(nπ) events. The differential cross section d ⁴ σ/dΩ_d dΩ _π ⁺ dp _d dp _π ⁺ for the reaction pp → dπ ⁺ η has been determined model independently for two regions of phase space. Employing a dynamical model for the a ₀ ⁺ production allows one then to deduce a total cross section of σ(pp → da ₀ ⁺ → dπ ⁺ η) = 1.1 ± 0.3_stat ± 0.7_syst μb for the production of π ⁺ η via the scalar a ₀ ⁺ (980) resonance and σ(pp → dπ ⁺ η) = 3.5 ± 0.3_stat ± 1.0_syst μb for the nonresonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction , the ratio of the total cross sections is , which is in agreement with branching ratios in the literature. The text was submitted by the authors in English.     

Quark-Antiquark states and their radiative transitions in terms of the spectral integral equation: Bottomonia

In the framework of the spectral integral equation, we consider the states and their radiative transitions. We reconstruct the interaction on the basis of data for the levels of the bottomonium states with J ^PC = 0⁻⁺, 1⁻⁻, 0⁺⁺, 1⁺⁺, 2⁺⁺ as well as the data for the radiative transitions γ (3S) → _γχbJ(2P) and γ(2S) → _γχbJ(1P) with J = 0, 1, 2. We calculate bottomonium levels with the radial quantum numbers n ≤ 6, their wave functions, and corresponding radiative transitions. The ratios Br[_χbJ(2P) → _γγ(2S)]/Br[_χbJ(2P) → _γγ(1S)] for J = 0, 1, 2 are found to be in agreement with data. We determine the component of the photon wave function using the data for the e ⁺ e ⁻ annihilation, e ⁺ e ⁻ → γ(9460), γ(10 023), γ(10 036), γ(10 580), γ(10 865), γ(11 019), and predict partial widths of the two-photon decays ηb0 → γγ, χb0 → γγ, χb2 → γγ for the radial excitation states below the threshold (n ≤ 3). The text was submitted by the authors in English.     

Spin observables of the reactions NN → Δ N and pd → Δ( pp )(1 S 0) in collinear kinematics

A general formalism for double and triple spin correlations of the reaction is developed for the case of collinear kinematics. A complete polarization experiment allowing one to reconstruct all four amplitudes describing this process is suggested. Furthermore, the spin observables of the inelastic charge-exchange reaction (pp)(¹ S ₀ are analyzed in collinear kinematics within the single pN-scattering mechanism involving the subprocess pn → Δ⁰ p. The full set of spin observables, related to the polarization of one or two initial particles and one final particle, is obtained in terms of three invariant amplitudes of the reaction pd → Δ(pp)(¹ S ₀) and the transition form factor d → (pp)(¹ S ₀). A complete polarization experiment for the reaction (pp)(¹ S ₀) is suggested which allows one to determine three independent combinations of the four amplitudes of the elementary subprocess . The text was submitted by the authors in English.     

Contribution of semi-hadronic states <Emphasis Type="Italic">P</Emphasis>γ, <Emphasis Type="Italic">S</Emphasis>γ, π<Superscript>+</Superscript>π<Superscript>−</Superscript>γ to amm of muon in the framework of the Nambu-Jona-Lasinio model

We calculate the contribution of semi-hadronic states with the pseudoscalar P = π⁰, η and scalar (σ(550)) meson accompanied with a real photon as an intermediate state of a heavy photon to the anomalous magnetic moment of the muon. We consider the intermediate states with π⁰ and σ as hadrons in the frame-work of the Nambu-Jona-Lasinio (NJL) model. The contribution of the π⁰γ state is in agreement with results obtained in previous theoretical considerations as well as with the experimental data $ a_\mu ^{\pi _0 \gamma } \approx 4.5 \times 10^{ - 10} $ a_\mu ^{\pi _0 \gamma } \approx 4.5 \times 10^{ - 10} , besides we estimate a _μ^ηγ = 0.7 × 10⁻¹⁰, a _μ^σγ ∼ 1.5 × 10⁻¹¹, $ a_\mu ^{\pi ^ + \pi ^ - \gamma } \sim 3.2 \times 10^{ - 10} $ a_\mu ^{\pi ^ + \pi ^ - \gamma } \sim 3.2 \times 10^{ - 10} . We also discuss the light-by-light (LbL) mechanism with a _μ ^lbl = 10.5 × 10⁻¹⁰.     

Direct photons in nuclear collisions at fair energies

Using the extrapolation of existing data, estimations of prompt-photon production at FAIR energies have been made. At y = y _c.m. the rapidity density of prompt photons with p _t > 1.5 GeV/c per central Au + Au event at 25 A GeV is estimated as ∼10⁻⁴. With the planned beam intensity 10⁹ per second and 1% interaction probability, for 10% of most central events one can expect the prompt-photon rate ∼10² photons per second. Direct photons from the hadron scenario of ion collisions generated by the Hadron-String-Dynamics (HSD) transport approach with implemented meson scatterings πρ → πγ, ππ → ργ have been analyzed. Photons from short-living resonances (e.g., ω → π ⁰ γ) decaying during the dense phase of the collision should be considered as direct photons. They contribute significantly in the directphoton spectrum at p _t = 0.5–1 GeV/c. At the FAIR energy 25 A GeV in Au + Au central collisions the HSD generator predicts, as a lower estimate, γ _direct/ ≃ 0.5% in the region p _t = 0.5–1 GeV/c. At p _t = 1.5–2 GeV/c γ _prompt/ ≃ 2%. Thermal direct photons have been evaluated with the Bjorken Hydro-Dynamics (BHD) model. The BHD spectra differ strongly from the HSD predictions. The direct-photon spectrumis very sensitive to the initial temperature parameter T ₀ of the model. The 10-MeV increase in the T ₀ value leads to ∼2 times higher photon yield. The text was submitted by the authors in English.     

Electromagnetic effects and scattering lengths extraction from experimental data on K → 3π decays

The final state interactions in K ^± → π^±π⁰π⁰ decays are considered using the methods of nonrelativistic quantum mechanics. It is shown how to take into account the largest electromagnetic effect in the analysis of experimental data using the amplitudes calculated earlier. The relevant expressions for amplitude corrections valid both above and below the two charged pions production threshold , including the average effect for the threshold bin, are proposed. These formulae can be used in the procedure of pion scattering lengths measurement from spectrum. The text was submitted by the authors in English.     

Multiplicity dependence of <Emphasis Type="Italic">z</Emphasis> scaling for identified hadrons

The multiplicity dependence of inclusive spectra of identified hadrons (π, K, , K _S ⁰ , and Λ) produced in high-energy p and pp collisions is studied. Analysis of experimental data on high-p _T hadron cross sections obtained at the Tevatron and RHIC is performed in the framework of z scaling. Independence of the scaling function ψ(z) on the multiplicity density dN _ch/dη is established. The multiplicity density measured in nucleon-nucleon collisions reaches much higher values than the corresponding quantity [1/(0.5N _p)]dN _ch/dη obtained in heavy-ion collisions. Its influence on particle production reveals properties of self-similarity and fractality. The relation between the scaling variable z and thermodynamic quantities (“heat capacity” and “temperature”) of the medium associated with the produced inclusive particle is discussed. Search for z-scaling violation in p and pp collisions at very high multiplicities as an indication of new-physics phenomena is suggested. The text was submitted by the authors in English.     

Can radiogenic heat sources inside the Earth be located by their antineutrino incoming directions?

Antineutrinos born in the U and Th decay chains inside the Earth (geoneutrinos) carry information on the amount and distribution of radiogenic heat sources, which is of fundamental importance for geophysics. Models of the Earth distribute U and Th masses mainly between the continental crust and the lower mantle. It has been much discussed recently that a number of detectors stationed at appropriate geographical sites can separate the crust and mantle contributions. We analyze directional separation of signals arriving from the crust and the lower mantle with only one detector. We find that, with an ∼ 30-kt liquid scintillation antineutrino spectrometer using the + p → e ⁺ + n detection reaction and positron and neutron coordinate reconstruction techniques, the U and Th distribution model can roughly be tested. We also consider detector calibration using an ∼ 1-MCi commercially available ⁹⁰Sr-⁹⁰Y beta source which emits (E _ν,max = 2.28 MeV) in the geoneutrino energy range. The text was submitted by the authors in English. Also at CEA/Saclay.     

Isospin and the tau hadronic decay modes

Isospin constraints onτ decay modes are revisited with a special interest for the low branching ratio channels. It is shown that dominance of the vector current in the channel is suggested by the present data and that some discrepancies exist betweenτ partial width ande ⁺ e ⁻ cross-section measurements in the 6π channel.