14533781
CP violating Z Z H coupling at e+ e- linear colliders
We study the general Higgs-weak boson coupling with CP-violation via the process e+e- -> f \bar f h. We categorize the signal channels by sub-processes Zh production and ZZ fusion and construct four CP asymmetries by exploiting polarized e+e- beams. We find complementarity among the sub-processes and the asymmetries to probe the real and imaginary parts of the CP-violating form factor. Certain asymmetries with unpolarized beams can retain significant sensitivity to the coupling. We conclude that at a linear collider with high luminosity, the CP-odd ZZh coupling may be sensitively probed via measurements of the asymmetries.
119090701
Axion models with high-scale supersymmetry breaking
Abstract Inspired by the possibility of high-scale supersymmetry breaking in the string landscape where the cosmological constant problem and the gauge hierarchy problem can be solved while the strong CP problem is still a challenge for naturalness, we propose a supersymmetric KSVZ axion model with an approximate universal intermediate-scale ( ∼ 10 11  GeV ) supersymmetry breaking. To protect the global Peccei–Quinn (PQ) symmetry against quantum gravitational violation, we consider the gauged discrete Z N PQ symmetry. In our model the axion can be a cold dark matter candidate, and the intermediate supersymmetry breaking scale is directly related to the PQ symmetry breaking scale. Gauge coupling unification can be achieved at about 2.7 × 10 16  GeV . The Higgs mass range is 130 to 160 GeV. We briefly discuss other axion models with high-scale supersymmetry breaking where the stabilization of the axion solution is similar.
118827473
Limits to solar cycle predictability: Cross-equatorial flux plumes
Context. Within the Babcock-Leighton framework for the solar dynamo, the strength of a cycle is expected to depend on the strength of the dipole moment or net hemispheric flux during the preceding minimum, which depends on how much flux was present in each hemisphere at the start of the previous cycle and how much net magnetic flux was transported across the equator during the cycle. Some of this transport is associated with the random walk of magnetic flux tubes subject to granular and supergranular buffeting, some of it is due to the advection caused by systematic cross-equatorial flows such as those associated with the inflows into active regions, and some crosses the equator during the emergence process. Aims. We aim to determine how much of the cross-equatorial transport is due to small-scale disorganized motions (treated as diffusion) compared with other processes such as emergence flux across the equator. Methods. We measure the cross-equatorial flux transport using Kitt Peak synoptic magnetograms, estimating both the total and diffusive fluxes. Results. Occasionally a large sunspot group, with a large tilt angle emerges crossing the equator, with flux from the two polarities in opposite hemispheres. The largest of these events carry a substantial amount of flux across the equator (compared to the magnetic flux near the poles). We call such events cross-equatorial flux plumes. There are very few such large events during a cycle, which introduces an uncertainty into the determination of the amount of magnetic flux transported across the equator in any particular cycle. As the amount of flux which crosses the equator determines the amount of net flux in each hemisphere, it follows that the cross-equatorial plumes introduce an uncertainty in the prediction of the net flux in each hemisphere. This leads to an uncertainty in predictions of the strength of the following cycle.
118692889
Determination of tan beta at a future e+e- linear collider
It is widely stated that the ratio of neutral Higgs field vacuum expectation values, $\tanb$, is one of the most difficult parameters to determine in either the Minimal Supersymmetric Standard Model (MSSM) or a general type-II Two-Higgs Doublet Model (2HDM). Assuming an energy and integrated luminosity of $\rts=500\gev$ and $\call=2000\fbi$, we show that a very accurate determination of $\tanb$ will often be possible using Higgs production rates and/or Higgs decays. Based on a TESLA simulation, and assuming no other light Higgs bosons and $100\leq m_A \leq 200\gev$, we find that the rate for the process $\epem\to b\anti b A \to b\anti b b\anti b$ provides an excellent determination of $\tanb$ at high $\tanb$. In the MSSM Higgs sector, the rate for $\epem\to b\anti b A+ b\anti b H \to b\anti b b\anti b$ ($\epem\to HA \to b\anti b b\anti b$) provides a good determination of $\tanb$ at high (low) $\tanb$, respectively, at moderate $m_A$ values. We also show that direct measurement of the average total width of the $H$ and $A$ in $\epem\to HA \to b\anti b b\anti b$ events provides an excellent determination of $\tanb$ at large $\tanb$.
1167548
SURFACE FLUX TRANSPORT MODELING FOR SOLAR CYCLES 15-21: EFFECTS OF CYCLE-DEPENDENT TILT ANGLES OF SUNSPOT GROUPS
We model the surface magnetic field and open flux of the Sun from 1913 to 1986 using a surface flux transport model, which includes the observed cycle-to-cycle variation of sunspot group tilts. The model reproduces the empirically derived time evolution of the solar open magnetic flux and the reversal times of the polar fields. We find that both the polar field and the axial dipole moment resulting from this model around cycle minimum correlate with the strength of the following cycle.
119415188
Signals for CP violation in split supersymmetry
Abstract Split supersymmetry is characterized by relatively light chargino and neutralino sector and very heavy sfermion sector. We study the consequence of CP violation in this scenario by evaluating two-loop contributions to electric dipole moments of fermions from Higgs-photon as well as W – W diagrams. These contributions add coherently and produce electron and neutron electric dipole moments close to present bounds. We then explore Higgs production at a photon–photon collider, and consider the feasibility of measuring CP violating h γ γ coupling induced by chargino loops. Methods of enhancing the sensitivity are discussed. For lower chargino masses and lower Higgs boson masses, the effect of the CP violation can be observed with 90% confidence level significance.
98476250
The Bi-2212 conductor and magnet program at the National High Magnetic Field Laboratory
The NHMFL has had a long running program to develop Bi2Sr2CaCu2Ox (Bi2212) for high field magnets. The recent development of round wire Bi2212 (RW2212) has strengthened the effort to develop solenoid magnets with fields substantially greater than can be achieved with Nb3Sn. The present paper briefly summarizes some of the results obtained at the NHMFL in the past 12 months. It summarizes the talk given by David Larbalestier at WAMSDO on May 24, 2008. Much of the work is ongoing and will be reported in the normal peer reviewed literature in late 2008.
118289508
A transformative superconducting magnet technology for fields well above 30 T using isotropic round wire multifilament Bi2Sr2CaCu2O8-x conductor
We report here that magnetic fields of almost 34 T, far above the upper 24 T limit of Nb3Sn, can be generated using a multifilament round wire conductor made of the high temperature cuprate superconductor Bi2Sr2CaCu2O8-x (Bi-2212). A remarkable attribute of this Bi-2212 conductor is that it does not exhibit macroscopic texture and contains many high angle grain boundaries but nevertheless attains very high superconducting critical current densities Jc of 2500 A/mm2 at 20 T and 4.2 K. This Bi-2212 conductor does not possess the extreme texture that high Jc coated conductors of REBa2Cu3O7-x (REBCO) require, avoiding also its high aspect ratio, large superconducting anisotropy and the inherent sensitivity to defects of a single filament conductor. Bi-2212 wires can be wound or cabled into almost any type of superconducting magnet and will be especially valuable for very high field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. This demonstration that grain boundary limits to high Jc can be practically overcome suggests the huge value of a renewed focus on grain boundary properties in non-ideal geometries, especially with the goal of translating the lessons of this Bi-2212 conductor into fabrication of multifilament round wire REBCO or Fe-based superconductors.
205409621
Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T.
Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J(c). To minimize such grain boundary obstacles, HTS conductors such as REBa2Cu3O(7-x) and (Bi, Pb)2Sr2Ca2Cu3O(10-x) are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi2Sr2CaCu2O(8-x) (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very high J(c) of 2,500 A mm(-2) at 20 T and 4.2 K. The large potential of the conductor has been demonstrated by building a small coil that generated almost 2.6 T in a 31 T background field. This demonstration that grain boundary limits to high Jc can be practically overcome underlines the value of a renewed focus on grain boundary properties in non-ideal geometries.
139229583
Tests of HTS insert coils above 30 T
Recently HTS insert coils have been operated in background magnetic fields over 30 T, reaching record values for the central magnetic field. One YBCO double pancake coil generated 2.8 T in a 31 T background for a total of 33.8 T. A Bi-2212 layer wound coil generated 1.1 T in a 31 T background for a total of 32.1 T. Here we report on the test set-up and the obtained results. Introduction •Goal: demonstrate the suitability of HTS conductors > 30 T •Two insert coils are built and tested in a background magnetic field of 31 T. 1) YBCO insert coil with commercial conductor from SuperPower Inc. 2) Bi-2212 coil using commercial φ 1 mm wire from Oxford Instruments, Superconducting Technology (OST). •Coils are wound and tested at the NHMFL in a 31 T resistive magnet with a 39 mm diameter cryostat. •HTS coils were protected with a quench detection system, circuit breakers and a 0.5 Ohm dump resistor units YBCO coil Bi-2212 coil Conductor 4 by 0.1 mm tape φ 1 mm wire Insulation varnish ceramic braid Impregnation none Epoxy VPI Conductor length m 36 66 Self-inductance mH 1.9 2.6 Field constant mT/A 8.7 9.1 Typical Ic A 120 A at 77 K, SF 330 A at 4.2 K, 5T