2,514 research outputs found
Chargino Production and Decay in Photon-Photon-Collisions
We study the production and leptonic decay of charginos in collisions of
polarized photon beams including the complete spin correlations. The photons
can be generated by Compton backscattering of polarized laser pulses off a
polarized electron beam. Since the production process is determined alone by
the electromagnetic coupling of the charginos this process allows to study
their decay dynamics. The cross section and the forward-backward asymmetry of
the decay lepton are very sensitive to the gaugino mass parameter and to
the sneutrino mass without any ambiguities.Comment: 9 pages, 6 figures, LaTeX, Talk presented at the International
Workshop on High Energy Photon Collider
Spin and spin-spin correlations in chargino pair production at future linear e+e- colliders
A possibility to measure the spin and spin-spin correlations of a chargino
pair is investigated in the process electron positron -> chargino_1
anti-chargino_1 -> (neutralino_1 quark anti-quark) (neutralino_1 quark
anti-quark) at future linear-collider energies. The total and the differential
cross sections are calculated by the GRACE system which allows for the full
spin correlation. Experimental sensitivity of the measurements are examined by
assuming the limited detector resolution, the initial state radiation and the
beam-beam effect (beamstrahlung). It is found that generally the spin-spin
correlation can only be measured with a lower sensitivity than the chargino
spin itself. The dependence of the correlation measurements on the relevant
SUSY parameters can be seen for a light sneutrino case, but the situation
becomes worse for a heavier sneutrino.Comment: 23 pages, 7 figures, 6 tables; added reference for section
GRACE/SUSY Automatic Generation of Tree Amplitudes in the Minimal Supersymmetric Standard Model
GRACE/SUSY is a program package for generating the tree-level amplitude and
evaluating the corresponding cross section of processes of the minimal
supersymmetric extension of the standard model (MSSM). The Higgs potential
adopted in the system, however, is assumed to have a more general form
indicated by the two-Higgs-doublet model. This system is an extension of GRACE
for the standard model(SM) of the electroweak and strong interactions. For a
given MSSM process the Feynman graphs and amplitudes at tree-level are
automatically created. The Monte-Carlo phase space integration by means of
BASES gives the total and differential cross sections. When combined with
SPRING, an event generator, the program package provides us with the simulation
of the SUSY particle productions.Comment: 39 page, 1 figur
Recommended from our members
The strontium molecular lattice clock: Vibrational spectroscopy with hertz-level accuracy
The immaculate control of atoms and molecules with light is the defining trait of modern experiments in ultracold physics. The rich internal degrees of freedom afforded by molecules enrich the toolbox of precision spectroscopy for fundamental physics, and hold great promise for applications in quantum simulation and quantum information science. A vibrational molecular lattice clock with systematic fractional uncertainty at the 14th decimal place is demonstrated for the first time, matching the performance of the earliest optical atomic clocks. Van der Waals dimers of strontium are created at ultracold temperatures and levitated by an optical standing wave, whose wavelength is finely tuned to preserve the delicate molecular vibrational coherence.
Guided by quantum chemistry theory refined by highly accurate frequency-comb-assisted laser spectroscopy, record-long Rabi oscillations were demonstrated between vibrational molecular states that span the entire depth of the ground molecular potential. Enabled by the narrow molecular clock linewidth, hertz-level frequency shifts were resolved, facilitating the first characterization of molecular hyperpolarizability in this context. In a parallel effort, deeply bound strontium dimers are coherently created using the technique of stimulated Raman adiabatic passage. Ultracold collisions of alkaline-earth metal molecules in the absolute ground state are studied for the first time, revealing inelastic losses at the universal rate.
This thesis reports one of the most accurate measurement of a molecule's vibrational transition frequency to date, which may potentially serve as a secondary representation of the SI unit of time in the terahertz (THz) band where standards are scarce. The prototypical molecular clock lays the important groundwork for future explorations into THz metrology, quantum chemistry, and fundamental interactions at atomic length scales
Post-tuberculous fibrosing mediastinitis: a review of the literature.
Fibrosing mediastinitis (FM) is a rare disease where there is thickening of the fibrous tissue in the mediastinum. While histoplasmosis is the the most common recognised cause, the link with tuberculosis (TB) has been rarely documented. We review the link between TB and FM, and describe a case of probable TB-related FM.Our case is of a 74-year-old man who presented with breathlessness 3 years after fully treated TB. Scans revealed a calcified soft tissue mass within the mediastinum, and a diagnosis of fibrosing mediastinitis resulting in pulmonary hypertension was made. Tests for histoplasmosis and IgG4 staining were negative. Surgical intervention was not felt to be beneficial, and he was treated with prednisolone and mycophenolate mofetil.In the review, we highlight the two forms of mediastinitis-granulomatous versus fibrous, and how these two entities may be on a spectrum of disease progression. We also explore the prevalence, clinical presentation, pathogenesis, imaging techniques and treatment options of TB-related FM
Impact of bosonic decays on the search for stau_2 and tau-sneutrino
We perform a detailed study of the decays of the heavier tau slepton (stau_2)
and tau-sneutrino (snu_tau) in the Minimal Supersymmetric Standard Model
(MSSM). We show that the decays into Higgs or gauge bosons, i.e. stau_2 ->
stau_1 + (h^0, H^0, A^0 or Z^0), stau_2 -> snu_tau + (H^- or W^-), and snu_tau
-> stau_1 + (H^+ or W^+), can be very important due to the sizable tau Yukawa
coupling and large mixing parameters of stau. Compared to the decays into
fermions, such as stau_2 -> tau + neutralino_i and stau_2 -> nu_tau +
chargino_j^-, these bosonic decay modes can have significantly different decay
distributions. This could have an important influence on the search for stau_2
and snu_tau and the determination of the MSSM parameters at future colliders.Comment: 12 pages, 3 figures, LaTeX2
Automatic Computation of Cross Sections in HEP
For the study of reactions in High Energy Physics (HEP) automatic computation
systems have been developed and are widely used nowadays. GRACE is one of such
systems and it has achieved much success in analyzing experimental data. Since
we deal with the cross section whose value can be given by calculating hundreds
of Feynman diagrams, we manage the large scale calculation, so that effective
symbolic manipulation, the treat of singularity in the numerical integration
are required. The talk will describe the software design of GRACE system and
computational techniques in the GRACE.Comment: 6 pages, Latex, ICCP
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