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
118714441
The NMSSM and string theory
Abstract We study the possibility of constructing the NMSSM from the heterotic string. String-derived NMSSMs are much more rare than MSSMs due to the extra requirement that there exist a light singlet which couples to the Higgs pairs. They share the common feature that the singlet self-interactions are typically suppressed, leading to either the “decoupling” or the Peccei–Quinn limit of the NMSSM. In the latter case, the spectrum contains a light pseudoscalar which may be relevant to the MSSM fine-tuning problem. We provide a Z 6 heterotic orbifold example of the NMSSM with approximate Peccei–Quinn symmetry, whose origin lies in the string selection rules combined with our choice of the vacuum configuration.
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.
119408018
Chargino Contributions to Epsilon and Epsilon-Prime
We analyze the chargino contributions to the K-\bar K mixing and epsilon-prime in the mass insertion approximation and derive the corresponding bounds on the mass insertion parameters. We find that the chargino contributions can significantly enlarge the regions of the parameter space where CP violation can be fully supersymmetric. In principle, the observed values of epsilon and epsilon-prime may be entirely due to the chargino -- up-squark loops.
3003989
Universal torsion-induced interaction from large extra dimensions
We consider the Kaluza-Klein (KK) scenario in which only gravity exists in the bulk. Without the assumption of symmetric connection, the presence of brane fermions induces torsion. The result is a universal axial contact interaction that dominates those induced by KK gravitons. This enhancement arises from a large spin density on the brane. Using a global fit to Z-pole observables, we find the 3sigma bound on the scale of quantum gravity to be 28 TeV for n = 2. If Dirac or light sterile neutrinos are present, the data from SN1987A increase the bound to sqrt[n] M(S)>/=210 TeV.
1934772
The CKM phase in heterotic orbifold models
Abstract We consider properties of the CKM phase in the heterotic orbifold models. We find that at the renormalizable level the CKM phase vanishes identically for the prime orbifolds, whereas it can be nonzero for some nonprime orbifolds. In particular, we study in detail the Z 6 -I orbifold which allows for a nontrivial CKM phase and analyze the modular properties of the corresponding Jarlskog invariant. The CKM phase is shown to vanish if the moduli fields are stabilized at Im T i =±1/2.
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.
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.
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.
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
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.