118645488
Signature splitting in 173W with triaxial particle rotor model
A particle rotor model with a quasi-neutron coupled with a triaxially deformed rotor is applied to study signature splitting for bands with intruder orbital ν7/2+[633] and nonintruder orbital ν5/2-[512] in 173W. Excellent agreement with the observed energy spectra has been achieved for both bands. Signature splitting for band ν7/2+[633], and band ν5/2-[512] before the onset of signature inversion, is satisfactorily reproduced by introducing the γ degree of freedom. The phase and amplitude of signature splitting in band ν5/2-[512] are attributed to strong competition between 2f7/2 and 1h9/2 components. However, the self-consistent explanation of signature inversion in band ν5/2-[512] is beyond the present one quasi-neutron coupled with a triaxially deformed rotor.
123285492
Examining B(M1) staggering as a fingerprint for chiral doublet bands
The electromagnetic transitions of the doublet bands with different triaxiality parameter gamma are discussed in the particle rotor model with pi Th(11/2) circle times vh(11/2)(-1) configuration. It is found that B(M1) staggering as well as the resulting B(M1)/B(E2) and B(M1)(in)/B(M1)(out) staggering are sensitive to the triaxiality parameter gamma, and they associate strongly with the characters of nuclear chirality for 15 degrees <= gamma <= 30 degrees, i.e., the staggering is weak in the chiral vibration region while strong in the static chirality region. For partner bands with near degenerate energy spectra and similar B(M1) and B(E2) transitions, the strong B(M1) staggering can be used as a fingerprint for the static chirality.
120766563
New insight into the shape coexistence and shape evolution of Yb-157
High-spin states in Yb-157 have been populated in the Sm-144( O-16,3n)Yb-157 fusion-evaporation reaction at a beam energy of 85 MeV. Two rotational bands built on the nu f(7/2) and nu h(9/2) intrinsic states, respectively, have been established for the first time. The newly observed nu f(7/2) band and previously known nu i(13/2) band in Yb-157 are discussed in terms of total Routhian surface methods and compared with the structures in the neighboring N = 87 isotones. The structural characters observed in Yb-157 provide evidence for shape coexistence of three distinct shapes: prolate, triaxial, and oblate. At higher spins, both the nu f(7/2) band and nu i(13/2) band in Yb-157 undergo a shape evolution with sizable alignments occurring.
113400995
Vorticity and magnetic field production in relativistic ideal fluids
In the framework of relativistic ideal hydrodynamics, we study the production mechanism for vorticity and magnetic field in relativistic ideal fluids. It is demonstrated that in the uncharged fluids the thermal vorticity will always satisfy the Kelvin's theorem and the circulation must be conserved. However, in the charged fluids, the vorticity and magnetic field can be produced by the interaction between the entropy gradients and the fluid velocity gradients. Especially, in the multiple charged fluids, the vorticity and magnetic field can be produced by the interaction between the inhomogeneous charge density ratio and the fluid velocity gradients even if the entropy distribution is homogeneous, which provides another mechanism for the production of vorticity and magnetic field in relativistic plasmas or in the early universe.
118485729
Chirality in odd-A Rh isotopes within the triaxial particle rotor model
By adopting the fully quantal triaxial particle-rotor model, the candidate chiral doublet bands in odd-A nuclei {sup 103}Rh and {sup 105}Rh with {pi}g{sub 9/2}{sup -1} x {nu}h{sub 11/2}{sup 2} configuration are studied. For the doublet bands in both nuclei, agreement is excellent for the observed energies over the entire spin range and B(M1)/B(E2) at higher spin range. The evolution of the chiral geometry with angular momentum is discussed in detail by using the angular momentum components and their probability distributions. Chirality is found to change from chiral vibration to nearly static chirality at spin I=37/2 and back to another type of chiral vibration at higher spin. The influence of the triaxial deformation {gamma} is also studied.
122825097
CHIRAL SYMMETRY IN ATOMIC NUCLEI
The significant progresses of the chirality in atomic nuclei are briefly reviewed for both experimental and theoretical sides. Chiral doublet bands beyond one-particle and one-hole coupled with a triaxial rotor as well as the possibilities of new phenomenon MχD are discussed.
28322811
Dynamical electron mass in a strong magnetic field
Motivated by recent interest in understanding properties of strongly magnetized matter, we study the dynamical electron mass generated through approximate chiral symmetry breaking in QED in a strong magnetic field. We reliably calculate the dynamical electron mass by numerically solving the nonperturbative Schwinger-Dyson equations in a consistent truncation within the lowest Landau level approximation. It is shown that the generation of dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass that explicitly breaks chiral symmetry in the absence of a magnetic field.
119247311
CHIRAL SYMMETRY BREAKING AND STABILITY OF THE MAGNETIZED VACUUM
The recent claim [arXiv:hep-th/0603070, arXiv:hep-th/0605020] that there exists in QED a maximum magnetic field of 10^{42} G, above which the magnetized vacuum becomes unstable with respect to the so-called "positronium collapse" is critically examined and unequivocally refuted.
118510255
BBU effect in an ERL-FEL two-purpose test facility
Both the Energy Recovery Linac (ERL) and Free Electron laser (FEL) are considered to be candidates of the fourth generation light source. It is proposed to combine FEL into an ERL facility to integrate the advantages of both ERL and FEL, and to realize a compact two-purpose light source. A test facility to verify this principle is being designed at the Institute of High Energy Physics, Beijing. One main concern is the beam breakup (BBU) instability which limits the available beam current. To this end, we developed a numerical simulation code to calculate the BBU threshold, which is found to have only a small reduction even in a high-FEL-bunch-charge operation mode, compared with that in the case with ERL bunches only. However, even with ERL beam current far below BBU threshold, we observed a fluctuation of the central orbit of the ERL bunches in the presence of FEL beam. We then present a physical model of BBU and understand the mechanism of the orbit-fluctuation in an ERL-FEL two-purpose machine. We found that by choosing an appropriate FEL bunch repetition rate, the central orbit fluctuation amplitude can be well controlled.
3580212
Search for anomalous production of multiple leptons in association with $W$ and $Z$ bosons at CDF
This paper presents a search for anomalous production of multiple low-energy leptons in association with a W or Z boson using events collected at the CDF experiment corresponding to 5.1 fb{sup -1} of integrated luminosity. This search is sensitive to a wide range of topologies with low-momentum leptons, including those with the leptons near one another. The observed rates of production of additional electrons and muons are compared with the standard model predictions. No indications of phenomena beyond the standard model are found. A 95% confidence level limit is presented on the production cross section for a benchmark model of supersymmetric hidden-valley Higgs production. Particle identification efficiencies are also provided to enable the calculation of limits on additional models.
12148304
Updated search for the standard model Higgs boson in events with jets and missing transverse energy using the full CDF data set
We present an updated search for the Higgs boson produced in association with a vector boson in the final state with missing transverse energy and two jets. We use the full CDF data set corresponding to an integrated luminosity of 9.45 fb−1 at a proton-antiproton center-of-mass energy of s√=1.96 TeV. New to this analysis is the inclusion of a b-jet identification algorithm specifically optimized for H→bb¯ searches. Across the Higgs boson mass range 90≤mH≤150 GeV/c2, the expected 95% credibility level upper limits on the VH production cross section times the H→bb¯ branching fraction are improved by an average of 14% relative to the previous analysis. At a Higgs boson mass of 125 GeV/c2, the observed (expected) limit is 3.06 (3.33) times the standard model prediction, corresponding to one of the most sensitive searches to date in this final state.