17840929
Torsion constraints in the Randall-Sundrum scenario
Torsion appears due to fermions coupled to gravity and leads to the strongest particle physics bounds on flat extra dimensions. In this work, I consider torsion constraints in the case of a warped extra dimension with brane and bulk fermions. From current data I obtain a $3\ensuremath{\sigma}$ bound on the TeV-brane mass scale ${\ensuremath{\Lambda}}_{\ensuremath{\pi}}g~2.2 (10) \mathrm{TeV}$ for the anti-de Sitter curvature $k=1(0.01)$ in (reduced) Planck units. If Dirac or light sterile neutrinos reside on the brane, the bound increases to 17 (78) TeV.
42733826
Electric dipole moments in the limit of heavy superpartners.
Supersymmetric loop corrections induce potentially large CP-violating couplings of the Higgs bosons to nucleons and electrons that do not vanish in the limit of heavy superpartners. The Higgs-mediated CP-odd four-fermion operators are enhanced by tan((3)beta and induce electric dipole moments of heavy atoms which exceed the current experimental bounds for the electroweak scale Higgs masses and tan(beta greater, similar 10. If only the first two sfermion generations are heavy, the Higgs-mediated contributions typically dominate over the Barr-Zee type two-loop diagrams at tan(beta>30.
43232371
CP -violating invariants in supersymmetry
I study the weak basis CP-violating invariants in supersymmetric models, in particular those which cannot be expressed in terms of the Jarlskog--type invariants, and find basis--independent conditions for CP conservation. With an example of the K-anti-K mixing, I clarify what are the combinations of supersymmetric parameters which are constrained by experiment.
17871990
Supersymmetry and electroweak leptonic observables
We study vertex corrections to the leptonic electroweak observables in the general minimal supersymmetric standard model at $\mathrm{tan}\ensuremath{\beta}\ensuremath{\lesssim}35.$ In particular, we address the question of whether supersymmetry can be responsible for the observed $2\ensuremath{\sigma}$ deviation from the standard model prediction in the invisible width of the Z. We find that the presence of a light (around 100 GeV) chargino and sleptons hinted by the ${g}_{\ensuremath{\mu}}\ensuremath{-}2$ measurements makes the agreement with experiment slightly better and improves the electroweak fit.
119349560
Constraints on two-Higgs-doublet models at large tan {beta} from W and Z decays
We study constraints on type-II two-Higgs-doublet models at large tan {beta} from CERN LEP and SLD Z-pole data and from lepton universality violation in W decay. We perform a global fit and find that, in the context of Z decay, the LEP-SLD experimental values for lepton universality violation, R{sub b}, and A{sub b} all somewhat disfavor the model. Contributions from the neutral-Higgs sector can be used to constrain the scalar-pseudoscalar Higgs mass splittings. Contributions from the charged-Higgs sector allow us to constrain the charged-Higgs boson mass. For tan {beta}=100 we obtain the 1{sigma} classical (Bayesian) bounds of m{sub H{sup {+-}}}{>=}670 GeV (370 GeV) and 1{>=}m{sub h{sup 0}}/m{sub A{sup 0}}|{sub {alpha}}{sub ={beta}}=m{sub H{sup 0}}/m{sub A{sup 0}}|{sub {alpha}}{sub =0}{>=}0.68 (0.64). The 2{sigma} bounds are weak. Currently, the Fermilab Tevatron experimental limits on lepton universality violation in W decay provide no significant constraint on the Higgs sector. (c) 2000 The American Physical Society.
16019794
A Stringy Solution to the FCNC Problem
The solution to the supersymmetric FCNC problem may not have a simple field theory interpretation. Here I advocate a possibility based on string selection rules. The requirement of non--trivial Yukawa structures restricts the form of the soft terms such that the FCNC problem often does not arise.
59025092
Decreasing transient beam loading in RF cavities of U-70 accelerator
The U-70 RF system was worked out to operate with the injector-linac at 100 MeV energy. A wide RF range was (2.6-6.1) MHz. For the U-70 injector Booster the wide RF range decreased and now it is (5.5-6.1) MHz. This fact and simplest method of changing the parameters in RF ferrite dominated cavities allow one to increase of the equivalent value of the cavity capacitance for the main frequency by about a factor of 2.7 and increase of the value of the cavity gap capacitance by about a factor of 5. The experimental investigation of the U-70 RF cavities due to the injection of bunches from the Booster into the U-70 orbit, near transition and on main flat-top is presented.
122053065
Coasting Beam in HERA-p Ring
This document is a report on stud ies of production/tr ansport mechanisms resulting in and of cures against a coasting beam halo observed at the HERA proton ring of DESY. Noises in the 208 MHz RF system, drift beyond RF buckets due to energy loss through synchrotron radiation of the highenergy protons and effect of adding the 52 MHz RF voltage are claimed to account for the diverse observations over the halation effect available by now. The work was performed under Attachment #63 to the Agreement between DESY (Hamburg, Germany) and IHEP (Protvino, Russia), re: Coasting Beam in HERA-p Ring, June 2000.
123386574
Experimental investigation of stochastic slow extraction from the U-70 synchrotron
The feasibility of developing a system for stochastic (noise) slow extraction from the U-70 proton synchrotron of the Institute for High Energy Physics is substantiated, and the results from its experimental testing are presented. The existing auxiliary 200-MHz RF system (accelerating frequency, 5.5–6 MHz) is used as a longitudinal kicker. This system is driven by the superposition of a deterministic (nonrandom) RF carrier and additive phase noise. The noise gives rise to longitudinal beam diffusion that forces protons into the third-order transverse extraction resonance. The technical constraints inherent in the U-70 machine are taken into account in the proposed scheme. The extraction technique is expected to provide flat-topped spills having a duration of a few seconds and a low contamination with ripple.
110736460
UPGRADING LONGITUDINAL BEAM BEHAVIOR IN IHEP BOOSTER
Operation of 1.5 GeV fast-cycling Booster proton synchrotron of IHEP has been long hampered by unwanted oscillations in bunch length. To identify the reason of such beam behavior, a dedicated beam-dynamics research program has been initiated. The scope of this activity has covered a variety of the might-be mechanisms behind — coherent instabilities, malfunction of voltage amplitude feedbacks, quality of the voltage program, etc. Ultimately, phase loop encircling the VCO has been upgraded, which resulted in a noticeably suppressed scale of both, dipole and quadrupole oscillations of beam. BEAM OBSERVATIONS Coherent oscillations in bunch length were incidentally observed during routine operation of the machine. These were monitored as a distortion of bunch shape prior to beam transfer. The process was accompanied by an occurrence of asymmetry in longitudinal density distribution. This picture had a rather uncertain cycle-to-cycle recurrence. Each time, the beam conduct was subject to improving noticeably with finer tuning the initial value of radio-frequency in the Booster. Still, a mismatch with phase-plane trajectories of the accepting ring, U70, persisted. It hampered subsequent accumulation and acceleration of a high intensity beam in U70. To this end, a dedicated R&D program was launched to study beam longitudinal oscillations through the entire cycle and elaborate technical cures against oscillations in bunch length, specifically.
115315717
Analysis of the Feedback-Loop Stability in the RF System of the U-70 Synchrotron
We present a systematic approach for investigating the stability of the accelerating system used in the U-70 proton synchrotron (Institute for High-Energy Physics). This system employs tunable ferrite-loaded cavities and is encircled by six feedback loops (both dedicated and spurious) with a cross-talk through a heavy beam loading, high accelerating rate, and the overlapping of the loop passbands. Ensuring the safety margin against self-excitation of the RF system imposes constraints on the limiting intensity of the beam that is accelerated in the synchrotron