531 research outputs found
Evaluation on the Effects of Deicing Chemicals on Soil and Water Environment
AbstractDeicing chemicals are widely used to clear the pavement snow in the cold areas of China and many other countries in winter, because of their simple operation and excellent snow-melting effect, which leads to more convenience for traffic and low probability of traffic accident in the city, especially in metropolis. However, with the ever-growing application of deicing chemicals, their negative effects on environment such as soil and water system increased dramatically. Based on the related researches in China and abroad, this paper summarized the two categories of deicing chemicals and their working principles, and then provided the unique characteristics of deicing chemicalsâ effects on soil and water environment in large cities, which may need considerable quantity of the chemicals to relieve traffic congestion. What's more, main aspects of impacts by deicing chemicals on regional soil and water environment and the fundamental factors related to the aspects above respectively were generalized, in order to propose a conceptual model to evaluate the harmful effects. Moreover, this paper put forward some suggestions for the further research in this field to fulfill the model, and provided a scientific basis for the pollution prevention of deicing chemicals on urban environment
Three heavy jet events at hadron colliders as a sensitive probe of the Higgs sector
Assuming that a non-standard neutral Higgs with an enhanced Yukawa coupling
to a bottom quark is observed at future hadron experiments, we propose a method
for a better understanding of the Higgs sector. Our procedure is based on
"counting" the number of events with heavy jets (where "heavy" stands for a c
or b jet) versus b jets, in the final state of processes in which the Higgs is
produced in association with a single high p_T c or b jet. We show that an
observed signal of the type proposed, at either the Tevatron or the LHC, will
rule out the popular two Higgs doublet model of type II as well as its
supersymmetric version - the Minimal Supersymmetric Standard Model (MSSM), and
may provide new evidence in favor of some more exotic multi Higgs scenarios. As
an example, we show that in a version of a two Higgs doublet model which
naturally accounts for the large mass of the top quark, our signal can be
easily detected at the LHC within that framework. We also find that such a
signal may be observable at the upgraded Tevatron RunIII, if the neutral Higgs
in this model has a mass around 100 GeV and \tan\beta > 50 and if the
efficiency for distinguishing a c jet from a light jet will reach the level of
50%.Comment: Revtex, 11 pages, 4 figures embedded in the text. Main changes with
respect to Version 1: Numerical results re-calculated using the CTEQ5L pdf,
improved discussion on the experimental consequences, new references added.
Conclusions remain unchanged. As will appear in Phys. Rev.
The role of Hall diffusion in the magnetically threaded thin accretion discs
We study role of the Hall diffusion in the magnetic star-disc interaction. In
a simplified steady state configuration, the total torque is calculated in
terms of the fastness parameter and a new term because of the Hall diffusion.
We show the total torque reduces as the Hall term becomes more significant.
Also, the critical fastness parameter (at which the total torque is zero)
reduces because of the Hall diffusion.Comment: Accepted for publication in Astrophysics and Space Scienc
Observation of Two New N* Peaks in J/psi -> and Decays
The system in decays of is limited to be
isospin 1/2 by isospin conservation. This provides a big advantage in studying
compared with and experiments which mix
isospin 1/2 and 3/2 for the system. Using 58 million decays
collected with the Beijing Electron Positron Collider, more than 100 thousand
events are obtained. Besides two well known
peaks at 1500 MeV and 1670 MeV, there are two new, clear peaks in
the invariant mass spectrum around 1360 MeV and 2030 MeV. They are the
first direct observation of the peak and a long-sought "missing"
peak above 2 GeV in the invariant mass spectrum. A simple
Breit-Wigner fit gives the mass and width for the peak as MeV and MeV, and for the new peak above 2 GeV
as MeV and MeV, respectively
Exclusive Higgs Boson Production with bottom quarks at Hadron Colliders
We present the next-to-leading order QCD corrected rate for the production of
a scalar Higgs boson with a pair of high p_T bottom and anti-bottom quarks at
the Tevatron and at the Large Hadron Collider. Results are given for both the
Standard Model and the Minimal Supersymmetric Standard Model. The exclusive
b-bbar-h production rate is small in the Standard Model, but it can be greatly
enhanced in the Minimal Supersymmetric Standard Model for large tan(beta),
making b-bbar-h an important discovery mode. We find that the next-to-leading
order QCD results are much less sensitive to the renormalization and
factorization scales than the lowest order results, but have a significant
dependence on the choice of the renormalization scheme for the bottom quark
Yukawa coupling.Comment: 27 pages, 17 figures, RevTeX
DAMA/LIBRA-phase1 results and perspectives of the phase2
The results obtained with the total exposure of 1.04 ton Ă yr collected by DAMA/LIBRAâphase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles are summarized. The DAMA/LIBRAâphase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton Ă yr, corresponding to 14 annual cycles) give evidence at 9.3 Ï C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade. The same data of DAMA/LIBRAâphase1 have also been analyzed searching for possible DM second-order diurnal effect; at present, the DM diurnal modulation amplitude â expected because of the Earth diurnal motion â evaluated on the basis of the DAMA Dark Matter annual modulation results is below the reached experimental sensitivity. Some of the perspectives of the presently running DAMA/LIBRAâphase2 are outlined
Possible implications of the channeling effect in NaI(Tl) crystals
The channeling effect of low energy ions along the crystallographic axes and
planes of NaI(Tl) crystals is discussed in the framework of corollary
investigations on WIMP Dark Matter candidates. In fact, the modeling of this
existing effect implies a more complex evaluation of the luminosity yield for
low energy recoiling Na and I ions. In the present paper related
phenomenological arguments are developed and possible implications are
discussed at some extent.Comment: 16 pages, 10 figures, preprint ROM2F/2007/15, submitted for
publicatio
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