830 research outputs found
Weakly coupled neutral gauge bosons at future linear colliders
A weakly coupled new neutral gauge boson forms a narrow resonance that is
hard to discover directly in e+e- collisions. However, if the gauge boson mass
is below the center-of-mass energy, it can be produced through processes where
the effective energy is reduced due to initial-state radiation and
beamstrahlung. It is shown that at a high-luminosity linear collider, such a
gauge boson can be searched for with very high sensitivity, leading to a
substantial improvement compared to existing limits from the Tevatron and also
extending beyond the expected reach of the LHC in most models. If a new vector
boson is discovered either at the Tevatron Run II, the LHC or the linear
collider, its properties can be determined at the linear collider with high
precision, thus helping to reveal origin of the new boson.Comment: 21 p
KrkNLO in Herwig 7
We validate and present new results from the first implementation of the KrkNLO method within the Herwig 7 event generator. In this work, we present numerical results for the Drell–Yan process, and Higgs-boson production via gluon fusion. The Drell–Yan process is used to validate this new implementation against the previous version in Sherpa, as well as to compare the recently introduced complete MC-scheme parton distribution functions to previous results. We present the first results of the KrkNLO method for Higgs production via gluon fusion at the LHC, and compare them to MC@NLO and POWHEG predictions from Herwig 7, as well as results from HNNLO and HqT
Jet analysis by Deterministic Annealing
We perform a comparison of two jet clusterization algorithms. The first one
is the standard Durham algorithm and the second one is a global optimization
scheme, Deterministic Annealing, often used in clusterization problems, and
adapted to the problem of jet identification in particle production by high
energy collisions; in particular we study hadronic jets in WW production by
high energy electron positron scattering. Our results are as follows. First, we
find that the two procedures give basically the same output as far as the
particle clusterization is concerned. Second, we find that the increase of CPU
time with the particle multiplicity is much faster for the Durham jet
clustering algorithm in comparison with Deterministic Annealing. Since this
result follows from the higher computational complexity of the Durham scheme,
it should not depend on the particular process studied here and might be
significant for jet physics at LHC as well.Comment: 15 pages, 4 figure
Markovian MC simulation of QCD evolution at NLO level with minimum k_T
We present two Monte Carlo algorithms of the Markovian type which solve the
modified QCD evolution equations at the NLO level. The modifications with
respect to the standard DGLAP evolution concern the argument of the strong
coupling constant alpha_S. We analyze the z - dependent argument and then the
k_T - dependent one. The evolution time variable is identified with the
rapidity. The two algorithms are tested to the 0.05% precision level. We find
that the NLO corrections in the evolution of parton momentum distributions with
k_T - dependent coupling constant are of the order of 10 to 20%, and in a small
x region even up to 30%, with respect to the LO contributions.Comment: 32 pages, 9 pdf figure
WW Cross-sections and Distributions
We present the results obtained by the "WW Cross-sections and Distributions"
working group during the CERN Workshop "Physics at LEP2" (1994/1995)Comment: 61 pages, tar'ed gzip'ed uuencoded files, LaTeX, 4 Postscript
figures. To appear in "Physics at LEP2", G.Altarelli and F.Zwirner eds., CERN
Report 199
The running of the electromagnetic coupling alpha in small-angle Bhabha scattering
A method to determine the running of alpha from a measurement of small-angle
Bhabha scattering is proposed and worked out. The method is suited to high
statistics experiments at e+e- colliders, which are equipped with luminometers
in the appropriate angular region. A new simulation code predicting small-angle
Bhabha scattering is also presentedComment: 15 pages, 3 Postscript figure
Precision Predictions for (Un)Stable W+W- Pair Production At and Beyond LEP2 Energies Beyond LEP2 Energies
We present precision calculations of the processes e+e- -> 4-fermions in
which the double resonant W+W- intermediate state occurs. Referring to this
latter intermediate state as the 'signal process', we show that, by using the
YFS Monte Carlo event generators YFSWW3-1.14 and KORALW1.42 in an appropriate
combination, we achieve a physical precision on the signal process, as isolated
with LEP2 MC Workshop cuts, below 0.5 per cent. We stress the full gauge
invariance of our calculations and we compare our results with those of other
authors where appropriate. In particular, sample Monte Carlo data are
explicitly illustrated and compared with the results of the program RacoonWW of
Dittmaier {\it et al.}. In this way, we show that the total (physical plus
technical) precision tag for the WW signal process cross section is 0.4 per
cent for 200 GeV, for example. Results are also given for 500 GeV with an eye
toward the LC.Comment: 19 pages, 2 figs;corrected Tab. 3;improved refs.,figs.,text;improved
refs.,text;improved tex
Extraction of emerging contaminants from environmental waters and urine by dispersive liquid-liquid microextraction with solidification of the floating organic droplet using fenchol:acetic acid deep eutectic mixtures
In this work, several eutectic mixtures formed by fenchol and acetic acid at seven molar ratios (between 4:1 and 1:4) were characterized and studied for the first time for their possible application as extraction solvents in dispersive liquid-liquid microextraction based on the solidification of the floating organic droplet (DLLME-SFO). A group of 13 emerging contaminants (gemfibrozil, bisphenol F, bisphenol A, 17β-estradiol, testosterone, estrone, levonorgestrel, 4-tert-octylphenol, butyl benzyl phthalate, dibutyl phthalate, 4-octylphenol, 4-nonylphenol, and dihexyl phthalate) was selected and determined by liquid chromatography with ultraviolet and tandem mass spectrometry detection. Among the studied mixtures, only those of 2:1 and 1:1 provided the suitable features from an operational and repeatability point of view, suggesting that several eutectic mixtures of the same components may also provide similar results. Once the extraction conditions of both mixtures were optimized, the method was applied to the extraction of sea water, urine, and wastewater at different concentration levels, allowing the achievement of absolute recovery values between 49 and 100% for most analytes with relative standard deviation values below 19%. In addition, several samples of each type were analyzed, finding bisphenol A and gemfibrozil in some of them. The greenness of the method was also evaluated using the AGREEprep metric. The DLLME-SFO procedure was found to be very simple, quick, and effective and with a good sample throughput
Sneutrino Mass Measurements at e+e- Linear Colliders
It is generally accepted that experiments at an e+e- linear colliders will be
able to extract the masses of the selectron as well as the associated
sneutrinos with a precision of ~ 1% by determining the kinematic end points of
the energy spectrum of daughter electrons produced in their two body decays to
a lighter neutralino or chargino. Recently, it has been suggested that by
studying the energy dependence of the cross section near the production
threshold, this precision can be improved by an order of magnitude, assuming an
integrated luminosity of 100 fb^-1. It is further suggested that these
threshold scans also allow the masses of even the heavier second and third
generation sleptons and sneutrinos to be determined to better than 0.5%. We
re-examine the prospects for determining sneutrino masses. We find that the
cross sections for the second and third generation sneutrinos are too small for
a threshold scan to be useful. An additional complication arises because the
cross section for sneutrino pair to decay into any visible final state(s)
necessarily depends on an unknown branching fraction, so that the overall
normalization in unknown. This reduces the precision with which the sneutrino
mass can be extracted. We propose a different strategy to optimize the
extraction of m(\tilde{\nu}_\mu) and m(\tilde{\nu}_\tau) via the energy
dependence of the cross section. We find that even with an integrated
luminosity of 500 fb^-1, these can be determined with a precision no better
than several percent at the 90% CL. We also examine the measurement of
m(\tilde{\nu}_e) and show that it can be extracted with a precision of about
0.5% (0.2%) with an integrated luminosity of 120 fb^-1 (500 fb^-1).Comment: RevTex, 46 pages, 15 eps figure
Radiative Correction to the Transferred Polarization in Elastic Electron-Proton Scattering
Model independent radiative correction to the recoil proton polarization for
the elastic electron-proton scattering is calculated within method of electron
structure functions. The explicit expressions for the recoil proton
polarization are represented as a contraction of the electron structure and the
hard part of the polarization dependent contribution into cross-section. The
calculation of the hard part with first order radiative correction is
performed. The obtained representation includes the leading radiative
corrections in all orders of perturbation theory and the main part of the
second order next-to-leading ones. Numerical calculations illustrate our
analytical results.Comment: 14 pages, 4 figure
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