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.
53956287
Upgrading the RF Cavity for U-70 Accelerator 0 -
This paper presents the results on the experimental invcstigation of the IJ-70 R.I: cavity with additional short circuit loops in thr RF magnetic field. These loops introduce a negative inductance impedanre into t,hc RF cavit,y circuit, and decreascx the cquivalcnt value of cavity inductance by about a factor of 10. This method allows at a low cost ‘,-fold increase the caparity of the accelerating gap for the 1!-70 cavity operating with the booster injection complex. ‘l’he lechnique of measuring the ferrite-dominated cavity pararncters is described.
182123800
Characteristics of Transversal Coherent Beam Instability on the Plateau of 386-Oe Magnetic Field at the SERPUKHOV Accelerator. (Talk, in Russian)
109125768
A feedback circuit for the stochastic extraction of protons from the U-70 synchrotron: Development and beam tests
Results of research efforts in 2005 that were directed toward developing a system for stochastic (noise) slow extraction of the beam from the U-70 proton synchrotron of the Institute for High Energy Physics are presented. The goal of the study was to develop a full-function prototype of the stochastic slow extraction system and test it on the beam. This prototype, designed for trial operation during machine runs, is capable of producing lengthy flat-topped smooth spills and suppressing their ripple. Approaches to design of the feedback loop that affects the waiting beam stack (which is neither a linear nor time-invariant system) are discussed. A circuit model of the beam being extracted is proposed and analyzed. A dedicated electronic system for beam experiments is described. Results of the beam tests during the U-70 machine run of 2005, which confirm the serviceability of the noise extraction system prototype, are presented.
126362745
A CAVITY FOR THE SECOND HARMONIC OF ACCELERATING-FIELD FREQUENCY IN THE IHEP SYNCHROTRON
117878917
Spontaneous CP-Violation in Two Higgs Doublet Supersymmetric Models
Physics (ABSTRACT) An alternative approach to the problem of CP-violation is presented. It is based on the possibility of spontaneous CP-breakdown in models with two Higgs doublets. General features of the phenomenon such as stability of the vacuum and the existence of a light axion are discussed. We investigate the feasibility of spontaneously broken CP in the minimal supersymmetric models-the MSSM and NMSSM. The latter is shown to be experimentally viable. The phenomenological implications of the model such as CP-violating effects in the kaon systems and a nonzero neutron electric dipole moment are studied. Acknowledgements I am deeply indebted to Prof. Lay Nam Chang for sharing his intimate knowledge of physics, his keen insight into fundamental problems and, constant support. I greatly appreciate the help and attention of the Department's secretaries in various matters. I am very grateful to the members of my Ph.D. committee for their supervision and efforts to make this work possible.
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.
8255616
Can Supersymmetry Soft Phases Be the Source of All CP Violation
Recently it has been demonstrated that large phases in softly broken supersymmetric theories are allowed by electric dipole moment constraints, and are motivated in some string models. Here we consider whether large soft phases in the supersymmetry breaking sector may be the dominant (or only) source of all CP violation, and demonstrate that ǫ and ǫ/ǫ can be described. We show that in the presence of large phases the SUSY contribution to the B system can be large and dominant, leading to predictions for b → sγ, sin 2β, and sin 2α. In this framework sin 2β/ sin 2α = −1, and the unitarity triangle does not close.
73589643
CP violation with Higgs-dependent Yukawa couplings
Abstract The framework of Higgs-dependent Yukawa couplings allows one to eliminate small couplings from the Standard Model, which can be tested at the LHC. In this work, I study the conditions for CP violation to occur in such models. I identify a class of weak basis invariants controlling CP violation. The invariant measure of CP violation is found to be more than 10 orders of magnitude greater than that in the Standard Model, which can be sufficient for successful electroweak baryogenesis.
17081623
Metastable vacua in flux compactifications and their phenomenology
In the context of flux compactifications, metastable vacua with a small positive cosmological constant are obtained by combining a sector where supersymmetry is broken dynamically with the sector responsible for moduli stabilization, which is known as the F-uplifting. We analyze this procedure in a model-independent way and study phenomenological properties of the resulting vacua.