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How Accurately Can We Measure the Reconnection Rate E M for the MMS Diffusion Region Event of 11 July 2017?
We investigate the accuracy with which the reconnection electric field E M can be determined from in situ plasma data. We study the magnetotail electron diffusion region observed by National Aeronautics and Space Administration's Magnetospheric Multiscale (MMS) on 11 July 2017 at 22:34 UT and focus on the very large errors in E M that result from errors in an L M N boundary normal coordinate system. We determine several L M N coordinates for this MMS event using several different methods. We use these M axes to estimate E M. We find some consensus that the reconnection rate was roughly E M = 3.2 ± 0.6 mV/m, which corresponds to a normalized reconnection rate of 0.18 ± 0.035. Minimum variance analysis of the electron velocity (MVA-v e), MVA of E, minimization of Faraday residue, and an adjusted version of the maximum directional derivative of the magnetic field (MDD-B) technique all produce reasonably similar coordinate axes. We use virtual MMS data from a particle-in-cell simulation of this event to estimate the errors in the coordinate axes and reconnection rate associated with MVA-v e and MDD-B. The L and M directions are most reliably determined by MVA-v e when the spacecraft observes a clear electron jet reversal. When the magnetic field data have errors as small as 0.5% of the background field strength, the M direction obtained by MDD-B technique may be off by as much as 35°. The normal direction is most accurately obtained by MDD-B. Overall, we find that these techniques were able to identify E M from the virtual data within error bars ≥20%
Magnetosheath High-Speed Jets: Internal Structure and InteractionWith Ambient Plasma
National Aeronautics and Space Administration (NASA). Grant Number: NNG04EB99C; Österreichische Forschungsförderungsgesellschaft (FFG); Austrian Academy of Sciences and the Austrian Space Applications Programme. Grant Number: FFG/ASAP-844377; NASA. Grant Numbers: NNX17AI45G, NAS5-02099; Austrian Science Fund (FWF). Grant Number: P 28764-N2
PGB pair production at LHC and ILC as a probe of the topcolor-assisted technicolor models
The topcolor-assisted technicolor (TC2) model predicts some light pseudo
goldstone bosons (PGBs), which may be accessible at the LHC or ILC. In this
work we study the pair productions of the charged or neutral PGBs at the LHC
and ILC. For the productions at the LHC we consider the processes proceeding
through gluon-gluon fusion and quark-antiquark annihilation, while for the
productions at the ILC we consider both the electron-positron collision and the
photon-photon collision. We find that in a large part of parameter space the
production cross sections at both colliders can be quite large compared with
the low standard model backgrounds. Therefore, in future experiments these
productions may be detectable and allow for probing TC2 model.Comment: 26 pages, 16 figures. slight changes in the text; notations for
curves changed; references adde
Electromagnetic form factor of pion from N_f=2+1 dynamical flavor QCD
We present a calculation of the electromagnetic form factor of the pion in
flavor lattice QCD. Calculations are made on the PACS-CS gauge field
configurations generated using Iwasaki gauge action and Wilson-clover quark
action on a lattice volume with the lattice spacing estimated as
fm at the physical point. Measurements of the form factor are
made using the technique of partially twisted boundary condition to reach small
momentum transfer as well as periodic boundary condition with integer momenta.
Additional improvements including random wall source techniques and a judicious
choice of momenta carried by the incoming and outgoing quarks are employed for
error reduction. Analyzing the form factor data for the pion mass at MeV and 296 MeV, we find that the NNLO SU(2) chiral perturbation
theory fit yields for the pion charge radius
at the physical pion mass. Albeit the error is quite large, this is consistent
with the experimental value of . Below MeV, we find that statistical fluctuations in the pion two- and
three-point functions become too large to extract statistically meaningful
averages on a spatial volume. We carry out a sample calculation on a
lattice with the quark masses close to the physical point, which
suggests that form factor calculations at the physical point become feasible by
enlarging lattice sizes to .Comment: 28 pages, 14 figure
Dijet resonances, widths and all that
The search for heavy resonances in the dijet channel is part of the on-going
physics programme, both at the Tevatron and at the LHC. Lower limits have been
placed on the masses of dijet resonances predicted in a wide variety of models.
However, across experiments, the search strategy assumes that the effect of the
new particles is well-approximated by on-shell production and subsequent decay
into a pair of jets. We examine the impact of off-shell effects on such
searches, particularly for strongly interacting resonances.Comment: Version published in JHE
LHC Predictions from a Tevatron Anomaly in the Top Quark Forward-Backward Asymmetry
We examine the implications of the recent CDF measurement of the top-quark
forward-backward asymmetry, focusing on a scenario with a new color octet
vector boson at 1-3 TeV. We study several models, as well as a general
effective field theory, and determine the parameter space which provides the
best simultaneous fit to the CDF asymmetry, the Tevatron top pair production
cross section, and the exclusion regions from LHC dijet resonance and contact
interaction searches. Flavor constraints on these models are more subtle and
less severe than the literature indicates. We find a large region of allowed
parameter space at high axigluon mass and a smaller region at low mass; we
match the latter to an SU(3)xSU(3)/SU(3) coset model with a heavy vector-like
fermion. Our scenario produces discoverable effects at the LHC with only 1-2
inverse femtobarns of luminosity at 7-8 TeV. Lastly, we point out that a
Tevatron measurement of the b-quark forward-backward asymmetry would be very
helpful in characterizing the physics underlying the top-quark asymmetry.Comment: 35 pages, 10 figures, 4 table
Quark masses and mixings in the RS1 model with a condensing 4th generation
We study the hierarchy of quark masses and mixings in a model based on a
5-dimensional spacetime with constant curvature of Randall-Sundrum type with
two branes, where the Electroweak Symmetry Breaking is caused dynamically by
the condensation of a 4th generation of quarks, due to underlying physics from
the 5D bulk and the first KK gluons. We first study the hierarchy of quark
masses and mixings that can be obtained from purely adjusting the profile
localizations, finding that realistic masses are not reproduced unless non
trivial hierarchies of underlying 4-fermion interactions from the bulk are
included. Then we study global U(1) symmetries that can be imposed in order to
obtain non-symmetric modified Fritzsch-like textures in the mass matrices that
reproduce reasonably well quark masses and CKM mixings.Comment: Minor changes. Version accepted for publication in JHE
Thin Current Sheet Behind the Dipolarization Front
We report a unique conjugate observation of fast flows and associated current sheet disturbances in the near-Earth magnetotail by MMS (Magnetospheric Multiscale) and Cluster preceding a positive bay onset of a small substorm at ∼14:10 UT, September 8, 2018. MMS and Cluster were located both at X ∼ −14 RE. A dipolarization front (DF) of a localized fast flow was detected by Cluster and MMS, separated in the dawn-dusk direction by ∼4 RE, almost simultaneously. Adiabatic electron acceleration signatures revealed from the comparison of the energy spectra confirm that both spacecraft encounter the same DF. We analyzed the change in the current sheet structure based on multi-scale multi-point data analysis. The current sheet thickened during the passage of DF, yet, temporally thinned subsequently associated with another flow enhancement centered more on the dawnward side of the initial flow. MMS and Cluster observed intense perpendicular and parallel current in the off-equatorial region mainly during this interval of the current sheet thinning. Maximum field-aligned currents both at MMS and Cluster are directed tailward. Detailed analysis of MMS data showed that the intense field-aligned currents consisted of multiple small-scale intense current layers accompanied by enhanced Hall-currents in the dawn-dusk flow-shear region. We suggest that the current sheet thinning is related to the flow bouncing process and/or to the expansion/activation of reconnection. Based on these mesoscale and small-scale multipoint observations, 3D evolution of the flow and current-sheet disturbances was inferred preceding the development of a substorm current wedge
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