126362745
A CAVITY FOR THE SECOND HARMONIC OF ACCELERATING-FIELD FREQUENCY IN THE IHEP SYNCHROTRON
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.
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.
126255062
EXPERIMENTAL STUDY OF COHERENT TRANSVERSE BEAM INSTABILITY AT THE IHEP ACCELERATOR
218611448
A STOCHASTIC SLOW EXTRACTION SCHEME FOR U70 SYNCHROTRON
Outcomes of a feasibility study for a low-budget stochastic slow extraction system in the U70 proton synchrotron of IHEP are reported. The existing 200 MHz (spill) RF system is to be employed as a longitudinal kicker. It will be driven by a sum of a non-random RF carrier plus an additive random amplitude-modulated signal — either quadrature or in-phase, or both. A few novel solutions to be implemented in the longitudinal diffusion technique that would force protons into the conventional 3-rd order transverse extraction resonance are foreseen so as to comply with the technical constraints inherent in U70. Getting a-few-seconds-long and high-quality spills is assessed as being viable with the system in question.
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
119440877
B Decays as a probe of spontaneous cp-violation in SUSY models
We consider phenomenological implications of susy models with spontaneously broken CP-symmetry. In particular, we analyze CP-asymmetries in B decays and find that the predictions of these models are vastly different from those of the SM. These features are common to NMSSM-like models with an arbitrary number of sterile superfields and the MSSM with broken R-parity.
14845868
CP PHENOMENOLOGY IN HETEROTIC STRING MODELS
I discuss aspects of the CP problem in heterotic orbifolds which arises in models with low energy supersymmetry. Recent measurements of the CP asymmetry in the B → ΨKs decay [1] imply that CP is significantly violated in nature and is not an approximate symmetry. Supersymmetric models with large CP phases generally predict fermion electric dipole moments (EDMs) that far exceed the experimental limits [2], and this presents a major challenge for low energy supersymmetry, the so called SUSY CP problem (see [3] for a review). In supergravity models, the soft supersymmetry breaking terms are functions of the hidden sector fields which enter the superpotential and the Kähler potential. In particular, the trilinear parameters are written as [4] Aαβγ = F [K̂m + ∂m log Yαβγ − ∂m log(K̃αK̃βK̃γ)] . (1) Here the Latin indices refer to the hidden sector fields while the Greek indices refer to the observable fields; the Kähler potential is expanded in observable fields as K = K̂ + K̃α|C| + ... and K̂m ≡ ∂mK̂. The sum in m runs over all of the SUSY breaking fields. We note that the supergravity notation for the A-terms and Yukawas can be connected to the “usual” one by fixing the order of the indices as follows: the first index is to refer to the Higgs fields, the second to the quark doublets, and the third to the quark singlets, e.g. YH1QiDj ≡ Y d ij . It is clear that if the auxiliary fields F are complex, the A-terms and other soft breaking terms will have complex phases. Such flavor-independent complex phases induce large EDMs, in conflict with experiment. This is the well known SUSY CP problem. This problem may seem to be circumvented by assuming that the F-terms are real. However, this is not case [5],[7]. First, let us note that in order to generate the Yukawa couplings hierarchy, these couplings must be functions of some scalar fields (e.g. moduli). Thus, the corresponding derivatives in (1) do not vanish. Now, if the auxiliary partners of these scalars break supersymmetry, e.g. F = 0, the resulting A-terms are non-universal or flavor–dependent. As a result, the soft trilinear parameters AαβγYαβγ are not diagonalized by the same transformations as the Yukawa matrices. So, in the physical (super-CKM) basis, the A-terms are not diagonal and their diagonal entries contain complex phases which result from diagonalization of the complex Yukawa matrices: ÛL,R → V u L,R ÛL,R , D̂L,R → V d L,R D̂L,R , 1332 Parallel Sessions Y u → V u T L Y u V u∗ R = diag(hu, hc, ht) , Y d → V d T L Y d V d∗ R = diag(hd, hs, hb) . (2) The strength of this effect can be estimated in the case of heterotic orbifolds. The matter fields must belong to the twisted sectors since otherwise the couplings are 1 or 0 and the mass hierarchy cannot be generated at the renormalizable level. The Yukawa coupling of the states at the fixed points f1,2,3 belonging to the twisted sectors θ1,2,3 is given by [6] Yf1f2f3 = N ∑ u∈Zn exp [ −4πT (f23 + u) M (f23 + u) ] . (3) where f23 ≡ f2 − f3, N is a normalization factor, and the matrix M (with fractional entries) is related to the internal metric of the orbifold. Here T is normalized such that T → T + i is a symmetry of the Lagrangian. For a realistic case, ReT = O(1), the sum is dominated by one term and ∂T lnYf1f2f3 −4π f23M f23 (4) for some (typically fractional) f23 depending on the positions of the fixed points. Unless F T is suppressed, this creates an order one non-universality in the A-terms which results in large EDMs (see [7] for numerical examples). In addition, this effect induces flavor changing neutral currents (FCNC). However the FCNC are not particularly sensitive to the flavor structure of the A-terms, so such effects are only subleading. This observation implies that either the flavor structure of the Yukawa matrices or the pattern of SUSY breaking is quite special. One possibility is that the supersymmetry breaking is dilaton–dominated. In this case, only F S is non-zero and the dangerous flavor effects disappear. To see whether this situation is possible in heterotic models, we analyze the vacua as functions of the dilaton S and an overall modulus T . To stabilize the dilaton, we use the non-perturbative Kähler potential KS = ln ( 1 2ReS + d(ReS) p 2 e−b √ ReS ) , (5) where d, p, b are certain constants (p, b > 0). To produce CP violation in the Yukawa couplings, e.g. to achieve a complex T at the minimum of the scalar potential, we multiply the standard gaugino condensate superpotential by a modular invariant function H(T ) = [ j(T ) − 1728 ]m 2 j(T ) n 3P [j(T )] , (6) where j(T ) is the absolutely modular invariant function, P [j(T )] is some polynomial of j(T ), and m,n are some negative fractional numbers. The results of the minimization of the scalar potential [8] are given in Table 1. We see that with appropriate m,n dilaton dominated SUSY breaking is possible. The corresponding SUSY parameters are flavor blind and the unwanted flavor mixing is absent. An interesting feature of this set-up is an axionic symmetry S → S + iα with a real continuous α. This means that the phase of the dilaton field is unphysical and S can 6: Supersymmetry and Superstrings 1333 δGS 0 1 1.5 m − 1 15 − 1 30 − 1 90 n − 2 15 − 2 30 − 2 90 Smin 1.75 1.71 1.69 Tmin 1.38 + 0.36i 1.45 + 0.44i 1.33 + 0.33i φ CKM O(1) O(1) O(1) V0/M 4 Pl 1.32 × 10−32 1.28 × 10−32 1.42 × 10−32 FS/Gev -2150 -2120 -2230 FT /Gev ∼ 0 ∼ 0 ∼ 0 Ma/Gev -604 -608 -646 mα/Gev 280 276 290 Aαβγ/Gev 169
5643336
Constraints on R-parity violating couplings from lepton universality
We analyze the one loop corrections to leptonic W and Z decays in an R-parity violating extension to the minimal supersymmetric standard model. We find that lepton universality violation in the Z line-shape variables alone would strengthen the bounds on the magnitudes of the {lambda}{sup '} couplings, but a global fit on all data leaves the bounds virtually unchanged at |{lambda}{sub 33k}{sup '}|{<=}0.42 and |{lambda}{sub 23k}{sup '}|{<=}0.50 at the 2{sigma} level. Bounds from W decays are less stringent: |{lambda}{sub 33k}{sup '}|{<=}2.4 at 2{sigma}, as a consequence of the weaker Fermilab experimental bounds on lepton universality violation in W decays. We also point out the potential of constraining R-parity violating couplings from the measurement of the {upsilon} invisible width. (c) 2000 The American Physical Society.
119110072
Higgs-induced lepton flavor violation
Abstract Due to the smallness of the lepton Yukawa couplings, higher dimensional operators can give a significant contribution to the lepton masses. In this case, the lepton mass matrix and the matrix of lepton–Higgs couplings are misaligned leading to lepton flavor violation (LFV) mediated by the Standard Model Higgs boson. We derive model-independent bounds on the Higgs flavor violating couplings and quantify LFV in decays of leptons and electric dipole moments for a class of lepton–Higgs operators contributing to lepton masses. We find significant Higgs-mediated LFV effects at both 1-loop and 2-loop levels.
16271509
De Sitter vacua from matter superpotentials
Consistent uplifting of AdS vacua in string theory often requires extra light degrees of freedom in addition to those of a (Kahler) modulus. Here we consider the possibility that de Sitter and Minkowski vacua arise due to hidden sector matter interactions. We find that, in this scheme, the hierarchically small supersymmetry breaking scale can be explained by the scale of gaugino condensation and that interesting patterns of the soft terms arise. In particular, a matter-dominated supersymmetry breaking scenario and a version of the mirage mediation scheme appear in the framework of spontaneously broken supergravity.