Hasil untuk "hep-ph"

M. Luo, Liucheng Wang, G. Zhu

Abstract It was observed recently that [L. Randall, Mark B. Wise, arXiv: 0807.1746 [hep-ph] ], any particle in the Standard Model cannot decay to e + e − and γγ final states with comparably measurable branching ratios. This is also true for most extensions of the Standard Model, with the Randall–Sundrum model as an outstanding exception. In this Letter, we show that two-Higgs-Doublet-Models (2HDM) yield another possible exception if certain parameters are properly chosen. In addition, we have checked that this model survives the tests of low energy processes, including the anomalous magnetic moment and electric dipole moment of leptons, lepton-flavor-violating decays μ − → e − γ and e − e + e − .

A. Ivanov, E. L. Kryshen, M. Pitschmann et al.

We give comments on the recent paper by Giunti (Phys. Lett. B 665, 92 (2008), arXiv: 0805.0431 [hep-ph]) with a critique of our explanation of the experimentally observed periodic time-dependence of the interference term in the rate of the K-shell electron capture decay of the H-like ions 140Pr58+ and 142Pm60+ as a two-neutrino-flavour mixing. We show also that this phenomenon cannot be explained by a coherent mixing of two states of a mother ion as proposed by Giunti.

F. Tkachov

The leading logarithmic approximation method fails to yield the correct asymptotic behavior in some realistic situations: inclusion of the beta-terms to which the LLA method is insensitive may change a power growth to merely logarithmic. The results of [hep-ph/0101058] indicate that the problem of large-s behavior of total cross sections belongs to this class. Similarly, a reference to the LLA method cannot be sufficient to justify constructions such as the kT jet algorithm.

Y. Kiyo

J. Amundson, C. Boyd, E. Jenkins et al.

F. Kleefeld

A self‐consistent strategy to complete the dynamical generation of Quark‐Level‐Linear‐Sigma‐Model‐like Lagrangean theories beyond one loop as proposed in more detail in our manuscript arXiv:0802.1540 [hep‐ph] [1] is shortly outlined.

E. Arganda, M. Herrero, J. Portolés et al.

In this paper we review our main results for Lepton Flavour Violating (LFV) semileptonic tau decays and muon-electron conversion in nuclei within the context of two Constrained SUSY-Seesaw Models, the CMSSM and the NUHM. The relevant spectrum is that of the Minimal Supersymmetric Standard Model extended by three right handed neutrinos, ν R i and their corresponding SUSY partners, ν ˜ R i , ( i = 1 , 2 , 3 ) . We use the seesaw mechanism for neutrino mass generation and choose a parameterisation of this mechanism that allows us to incorporate the neutrino data in our analysis of LFV processes. In addition to the full one-loop results for the rates of these processes, we will also review the set of simple formulas, valid at large tan β , which are very useful to compare with present experimental bounds. The sensitivity to SUSY and Higgs sectors in these processes will also be discussed. This is a very short summary of the works in Refs. [E. Arganda, M. J. Herrero and J. Portoles, JHEP 0806 (2008) 079 [ arXiv:0803.2039 [hep-ph] ]] and [E. Arganda, M. J. Herrero and A. M. Teixeira, JHEP 0710 (2007) 104 [ arXiv:0707.2955 [hep-ph] ]] to which we refer the reader for more details.

Alper Hayreter

Abstract The supersymmetric models extending the minimal supersymmetric Standard Model (MSSM) by an additional Abelian gauge factor U ( 1 ) ′ in order to solve the μ problem do generically suffer from anomalies disrupting the gauge coupling unification found in the MSSM. The anomalies are absent if the minimal matter content necessitated by the μ problem is augmented with exotic matter species having appropriate quantum numbers. Recently, it has been shown that anomaly cancellation can also be accomplished by introducing family non-universal U ( 1 ) ′ charges and non-holomorphic soft-breaking terms [D.A. Demir, G.L. Kane, T.T. Wang, Phys. Rev. D 72 (2005) 015012, hep-ph/0503290]. We discuss collider signatures of anomaly-free family non-universal U ( 1 ) ′ model by analyzing dilepton production in future colliders. We find that, both at LHC and NLC, one can establish existence/absence of such a Z ′ boson by simply comparing the number of dilepton production events for electron, muon and tau lepton. The signal is free of the SM background.

A. D. Felice

D. Frank

D.Yu.Grigoriev, F.V.Tkachov

We describe an efficient implementation of the optimal jet definition derived in hep-ph/9901444 (revision of January, 2000) and implemented in Fortran 77. The algorithm handles both c.m.s. and hadron collision kinematics.

Kin-ya Oda

F. Tkachov

Discussed is the structure of non-trivial counterterms that occur in the systematic gauge-invariant perturbation theory with unstable fields introduced in [hep-ph/9802307].

V. Khoze

It has been recently suggested in hep-ph/9911535 and hep-ph/0006324 that the fourth generation of leptons and quarks is not excluded by the precision Z-boson measurements, provided that the mass of the fourth neutrino is around 50 GeV and that its mixing with the neutrinos of the first three generations is negligibly small. We would like to note that in this case the decay rate of the Standard Model Higgs boson into the pair of such neutrinos would be about two orders of magnitude higher than than the Higgs to b-bbar rate. Thus, the predominant decay mode of the Higgs would be invisible, which would require a special strategy for its searches.

R. Plaga

Please see revised version hep-ph/0108052. The ps version of the manuscript contains the original abstract and body.

P. Ball

S. Narison

I report here on the (first) direct extraction of the running charm quark mass m_c(\nu) from the D-meson sum rules, and on the implications of this result for the estimate of the leptonic decay constants f_{D_s}. The outputs: m_c(M_c)=(1.08\pm 0.11) GeV, f_{D}= (1.52\pm 0.16)f_\pi, f_{D_s}= (1.75\pm 0.18)f_\pi and f_B=(1.44\pm 0.07)f_\pi are in good agreement with the existing sum rule results obtained using the pole mass. In particular, the result f_D\approx f_B supports early '87 sum rule results \cite{SNFB}, which indicated a huge 1/m correction to the heavy quark symmetry expectation. This talk is based on the paper hep-ph/9712386 and updates the discussions given there.

B. El-Bennich, O. Leitner, B. Loiseau et al.

Decay amplitudes of D ( D s ) → f 0 ( 980 ) X , X = π , K , are compared to experimental branching ratios with the aim of singling out the poorly known D → f 0 ( 980 ) transition form factor in these amplitudes. Since the other elements of the amplitudes are either calculable in an effective QCD theory using operator product expansion or are known from experiment (e.g. the pion and kaon decay constants), we can take advantage of these reactions to constrain the transition form factors obtained in relativistic quark models [O.M.A. Leitner, B. El-Bennich, B. Loiseau and J.-P. Dedonder, hep-ph/0609062 ; B. El-Bennich, O.M.A. Leitner, B. Loiseau and J.-P. Dedonder, hep-ph/0609154 ]. In these models, the f 0 ( 980 ) wavefunction requires an unknown size parameter for both its non-strange u ¯ u ( d ¯ d ) and strange s ¯ s components, which we fit to the D ( D s ) decay data.

S. Alexander, R. Brandenberger, R. Easther

We study the interaction between stable monopoles and domain walls in a $SO(3) \times Z(2)$ scalar field theory. Numerical simulations reveal that there is an attractive force between the monopole and the wall, but that after the monopole and the wall collide, the monopole does not unwind. We present an analytic explanation for the origin of the attractive force, and conclude that this is a generic feature of monopole-wall interactions which does not depend on the detailed structure of the model. The existence of the attractive force supports the hypothesis of Dvali {\em et al.} (hep-ph/9710301), who proposed that monopoles can be ``swept up'' by domain walls, thereby alleviating or solving the monopole problem associated with phase transitions occurring after or in the absence of inflation.

J. Bordes, H. Chan, S. Tsou

This paper is subsumed and superseded by hep-ph/0111175.