Possible galactic sources of ultrahigh-energy cosmic rays and a strategy for their detection via gravitational lensing

If decays of superheavy relic particles in the galactic halo are responsible for ultrahigh-energy cosmic rays, these particles must be clustered to account for small-scale anisotropy in the AGASA data. We show that the masses of such clusters are large enough for them to gravitationally lens stars and galaxies in the background. We propose a general strategy that can be used to detect such clusters via gravitational lensing, or to rule out the hypothesis of decaying relic particles as the origin of highest energy cosmic rays.     

Direct detection constraints on superheavy dark matter

The dark matter in the Universe might be composed of superheavy particles (mass greater, similar 10(10) GeV). These particles can be detected via nuclear recoils produced in elastic scatterings from nuclei. We estimate the observable rate of strongly interacting supermassive particles (simpzillas) in direct dark matter search experiments. The simpzilla energy loss in Earth and in the experimental shields is taken into account. The most natural scenarios for simpzillas are ruled out based on recent EDELWEISS and CDMS results. The dark matter can be composed of superheavy particles only if these interact weakly with normal matter or if their mass is above 10(15) GeV.     

Search for doubly charged Higgs bosons with lepton-flavor-violating decays involving tau leptons

We search for pair production of doubly charged Higgs particles (H+/- +/-) followed by decays into electron-tau (etau) and muon-tau (mutau) pairs using data (350 pb(-1) collected from [over]pp collisions at sqrt[s]=1.96 TeV by the CDF II experiment. We search separately for cases where three or four final-state leptons are detected, and combine results for exclusive decays to left-handed etau (mutau) pairs. We set an H+/- +/- lower mass limit of 114(112) GeV/c(2) at the 95% confidence level.     

Search for unstable heavy and excited leptons at LEP2

Searches for unstable neutral and charged heavy leptons, N and , and for excited states of neutral and charged leptons, , , , and , have been performed in collisions using data collected by the OPAL detector at LEP. The data analysed correspond to an integrated luminosity of about 58 pb at a centre-of-mass energy of 183 GeV, and about 10 pb each at 161 GeV and 172 GeV. No evidence for new particles was found. Lower limits on the masses of unstable heavy and excited leptons are derived. From the analysis of charged-current, neutral-current, and photonic decays of singly produced excited leptons, upper limits are determined for the ratio of the coupling to the compositeness scale, , for masses up to the kinematic limit. For excited leptons, the limits are established independently of the relative values of the coupling constants f and . Received: 29 November 1999 / Published online: 6 March 2000     

Generations of massless composite quarks and leptons

We present a QCD-like composite model in which quarks, leptons and technifermions are three-body systems made out of three kinds of massless elementary fermions t, c and w, each carrying technicolor, color and weak gauge interactions, respectively. Discrete symmetries, remnants of the U(1)_A of the original lagrangian, are responsible for the masslessness of all the quarks and leptons and give the precise meaning of the generations. The model exhibits three generations for both quarks and leptons. Small but non-zero masses of the quarks and leptons are produced by the technicolor condensate of the composite technifermions, which thereby leads to the non-trivial Cabibbo mixing. Proton decays are all forbidden at the mass scale of the QCD-like theory.     

Radiative corrections to semileptonic decays of charged hyperons

We have studied the radiative corrections to the lepton energy spectrum in semileptonic hyperon decays. The calculation is performed relativistically for the baryons as well as for the leptons, under the assumption of the effective current-current interaction of the V-?A type for the baryonic part. We obtain the explicit formula of radiative corrections to the lepton energy spectrum which we can exactly evaluate in case of charged hyperon decays. Numerical values of the radiative corrections to the decays rate and the shape of the lepton energy spectrum are also given for some decay modes. It is shown that the spectral shape is little affected by the radiative corrections.     

SU(4) weak currents

We suggest SU_L(4) ? U(1) as the gauge symmetry of weak and electromagnetic interactions for quartets of quarks and leptons. We analyze how the (additional) SU_L(4) weak currents (besides the SU_L(2) subgroup) could affect the weak interactions of ordinary particles, the atomic parity violation, the neutral-current neutrino reactions and the decays of the τ heavy lepton and the charmed mesons. The suppression of neutral-current parity violation in atomic experiments can be naturally incorporated in this model while at the same time the success of the Weinberg-Salam model with respect to the inclusive neutral current data is kept. The model has limited freedom and therefore many definite predictions.     

Measuring supersymmetry at the large hadron collider

The large hadron collider (LHC) should have the ability to detect supersymmetric particles if low-energy supersymmetry solves the hierarchy problem. Studies of the LHC detection reach, and the ability to measure properties of supersymmetric particles are currently underway. We highlight some of these, such as the reach in minimal supergravity space and correlation with a fine-tuning parameter, precision measurements of edge variables, anomaly or gauge-mediated supersymmetry breaking. Supersymmetry with baryon-number violation seems at first glance more difficult to detect, but proves to be possible by using leptons from cascade decays.     

Search for new physics in lepton+photon+X events with 305 pb(-1) of pp collisions at [square root of s] = 1.96 TeV

We present results of a search for anomalous production of events containing a charged lepton (l, either e or mu) and a photon (gamma), both with high transverse momentum, accompanied by additional signatures X, including missing transverse energy (ET) and additional leptons and photons. We use the same selection criteria as in a previous CDF search but with a substantially larger data set, 305 pb(-1), a pp collision energy of 1.96 TeV, and the CDF II detector. We find 42 lgammaET events versus an expectation of 37.3+/-5.4 events. We observe 31 llgamma+X events versus an expectation of 23.0+/-2.7 events. We find no events similar to the run I eegammagammaET event.     

Indications of a four-quark structure for the X(3872) and X(3876) particles from recent Belle and BABAR data

Recent results by Belle and BABAR point to the existence of a second X particle decaying in D(0)D(0)pi(0), a few MeV above the X(3872). We identify the two X states with the neutral particles predicted by the four-quark model and show that production and decays are consistent with this assignment. We consider the yet-to-be-observed charged partners and give new hints on how to look for them.     

Measurement of Wgamma and Zgamma production in pp collisions at square root s=1.96 TeV

The standard model predictions for Wgamma and Zgamma production are tested using an integrated luminosity of 200 pb(-1) of pp collision data collected at the Collider Detector at Fermilab. The cross sections are measured by selecting leptonic decays of the W and Z bosons, and photons with transverse energy ET>7 GeV that are well separated from leptons. The production cross sections and kinematic distributions for the Wgamma and Zgamma data are compared to SM predictions.     

Lepton number violation at the LHC with leptoquark and diquark

We investigate a model in which tiny neutrino masses are generated at the two-loop level by using scalar leptoquark and diquark multiplets. The diquark can be singly produced at the LHC, and it can decay into a pair of leptoquarks through the lepton number violating interaction. Subsequent decays of the two leptoquarks can provide a clear signature of the lepton number violation, namely two QCD jets and a pair of same-signed charged leptons without missing energy. We show that the signal process is not suppressed while neutrino masses are appropriately suppressed.     

Ultrahigh-energy cosmic rays, superheavy long-lived particles, and matter creation after inflation

Cosmic rays of the highest energy, above the Greisen-Zatsepin-Kuzmin (GZK) cutoff of the spectrum, may originate in decays of superheavy long-lived particles. We conjecture that these particles may be produced naturally in the early Universe from vacuum fluctuations during inflation and may constitute a considerable fraction of cold dark matter. We predict a new cutoff in the ultrahigh-energy cosmic ray spectrum E _cutoff<m _inflaton≈10¹³ GeV, the exact position of the cutoff and the shape of the cosmic ray spectrum beyond the GZK cutoff being determined by the QCD quark/gluon fragmentation. The Pierre Auger Project installation may in principle observe this phenomenon. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 255–259 (25 August 1998)     

Photon signatures for low energy supersymmetry breaking and broken R-parity

The possible phenomenological consequences of R-parity violating interactions in the framework of low energy supersymmetry breaking are studied. It is pointed out that even very weak R-parity violation would completely overshadow one of the basic signatures of low energy supersymmetry breaking models, that is the decay of the next to lightest supersymmetric particle into a photon (lepton) and missing energy. Thus, the observation of these decays would put very strong limits on R-parity violating couplings. Vice-versa, if R-parity violation is established experimentally, before a detailed knowledge of the spectrum is obtained, it will be very difficult to distinguish gravity mediated from low energy gauge mediated supersymmetry breaking scenarios. Those conclusions are very model independent. We also comment on the possibility of mixing between charged and neutral leptons with charginos and neutralinos, respectively, and its phenomenological consequences for the photon (lepton) signatures, in scenarios where this mixing is generated by the presence of bilinear or trilinear R-parity violating terms in the superpotential.     

Neutrino decays of hadrons and the conservation laws of quantum numbers

The main considerations and the quantitative data on the lifetimes of particles against neutrino decay are presented in support of an idea advanced previously by the present author concerning the leptonic origin of hadrons. According to this idea, neutrino decays of hadrons follow naturally from the decays of leptons entering into the hadronic structure. In the conclusion of the article it is shown that certain laws of conservation of quantum numbers observed in particle interactions as well as departures from the laws are specified by the initial premises of the muonic model of hadrons. The model necessitates a review of the accepted particle classification.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 22–27, August, 1978.     

SU(2)×U(1) effects in e+e− annihilation: Generalized charge asymmetry

The observability of the SU(2)×U(1) electroweak charge asymmetry effects in e⁺e^? annihilation at $\text{s}\text{=29}\text{GeV}$ is addressed in the context of a Feynman-Field type fragmentation model. We assume three colors of five flavored quarks and one heavy lepton τ. We neglect, at this time, the hard gluon bremsstrahlung events. We take b→c+X as the b-decay mode and we assume all τ's and heavy hadrons decay within the resolution of the detector so thatonly light hadrons and leptons are detected. Allowing all these decays to occur, we then compute the expected front-back asymmetry of negatively charged particles weighted with zⁿ for z?0.0175, where n = 0.5, 1…, 7, 10, and z is the light-cone momentum fraction. We find, for example, that such an asymmetry is ≈5% for n=2for sin²θ_w=0.236 and Λ_{QCD=0.34 GeV}. In other words, due to the large number of charge particles produced per event, this SU(2)×U(1) charge asymmetry may be accessible experimentally in e⁺e^? → X already at PEP and PETRA energies.     

超重核的基态性质

用Skyrme Hartree Fock+BCS方法计算了超重核的基态性质,讨论了结合能、α衰变、形变、壳结构和自发裂变等问题.计算得到的结合能较好地反映了实验测量值,α衰变能与实验值符合很好.发现基本上有两种类型的超重核形变:在270108核附近的β2≈0.2的长椭球形变和在298114核附近的近球形形变.单粒子能级分布计算表明:在质子Z=108和中子N=162存在变形壳,在质子Z=114和中子N=184存在球形壳.用得到的α衰变能和Viola Seaborg公式估算了α衰变半寿命,能合理地符合实验测量值. The ground state properties of superheavy nuclei are investigated using the Skyrme Hartree Fock model. The pairing correlation is treated by the BCS method with the pairing δ force. Binding energies, α decays, spontaneous fissions, shell structures and deformations are discussed. Our calculations reproduce experimential binding energies and α decay energies.It is found that superheavy nuclei can be grouped with two kinds of deformations: i) well deformed prolate shapes (β2≈0.2) around 270108...     

Measurement of theZ0 line shape parameters and the electroweak couplings of charged leptons

We report on an improved measurement of the mass of theZ ⁰ boson, its total width and its partial decay widths into hadrons and leptons, as well as the effective axial vector and vector couplings to charged leptons. These measurements are based on a data set of approximately 160 000 hadronicZ ⁰ decays and 18 000 decays into electrons, muons and taus, recorded by the OPAL experiment at centre of mass energies near the mass of theZ ⁰. The total width and the partial widths to visible final states, derived from the measured cross sections, are used to extract the invisible width. The effective couplings of theZ ⁰ to charged leptons are studied using measurements of the lepton pair cross sections and forward-backward asymmetries at the different centre of mass energy points of theZ ⁰ scan. The implications of our results in the context of the Standard Model are discussed.On leave from Research Institute for Computer Peripherals, Hangzhou, China     

Testing the Lorentz structure of the charged weak current in τ-decays

We review the current experimental situation on the determination of the Lorentz structure of the charged weak current in τ decays. We propose a method to extent these studies to decays of τ leptons to righthanded daughter leptons which are forbidden in the standard model. We reanalyse the available data in the framework of specific models and derive limits on the mass of charged Higgs bosons of m(H ^±) > 1.5 tan β GeV at 90 % c.l. and on righthanded W-bosons of m(W ₂) > 230 GeV at 90 % c.l., valid if the righthanded neutrinos associated with it are light compared to the τ.