236 research outputs found
Resonant production of diquarks at high energy pp, ep and e+e- colliders
Resonant productions of the first generation scalar and vector diquarks at
high energy hadron-hadron (pp), lepton-hadron (ep) and lepton-lepton (e+e-)
colliders are investigated. Taking into account the hadronic component of the
photon, diquarks can be produced resonantly in the lepton-hadron and
lepton-lepton collisions. Production rates, decay widths and signatures of
diquarks are discussed using the general, SU(3)_{C} x SU(2)_{W} x U(1)_{Y}
invariant, effective Lagrangian. The corresponding dijet backgrounds are
examined in the interested invariant mass regions. The attainable mass limits
and couplings are obtained for the diquarks that can be produced in hadron
collisions and in resolved photon processes. It is shown that hadron collider
with center of mass energy sqrt(s)=14 TeV will be able to discover scalar and
vector diquarks with masses up to m_{DQ}=9 TeV for quark-diquark-quark coupling
alpha_{DQ}=0.1. Relatively, lighter diquarks can be probed at ep and e+e-
collisions in more clear environment.Comment: 12 pages, 12 figures, 6 table
Mandelstam cuts and light-like Wilson loops in N=4 SUSY
We perform an analytic continuation of the two-loop remainder function for
the six-point planar MHV amplitude in N=4 SUSY, found by Goncharov, Spradlin,
Vergu and Volovich from the light-like Wilson loop representation. The
remainder function is continued into a physical region, where all but two
energy invariants are negative. It turns out to be pure imaginary in the
multi-Regge kinematics, which is in an agreement with the predictions based on
the Steinmann relations for the Regge poles and Mandelstam cut contributions.
The leading term reproduces correctly the expression calculated by one of the
authors in the BFKL approach, while the subleading term presents a result, that
was not yet found with the use of the unitarity techniques. This supports the
applicability of the Wilson loop approach to the planar MHV amplitudes in N=4
SUSY.Comment: 11 pages, 4 figure
Radiative corrections to the background of decay
Radiative muon decay in the kinematics similar to the neutrinoless decay
is considered. Radiative corrections due to 1-loop virtual
photons and emission of additional soft or hard photons are taken into account.
Analytical expressions and numerical estimations are presented.Comment: 11 pages, LaTeX, misprints in Eqs.(9,12,14) fixe
High energy scattering in 2+1 QCD
High energy scattering in 2+1 QCD is studied using the recent approach of
Verlinde and Verlinde. We calculate the color singlet part of the quark-quark
scattering exactly within this approach, and discuss some physical implication
of this result. We also demonstrate, by two independent methods, that
reggeization fails for the color singlet channel. We briefly comment on the
problem in 3+1 QCD.Comment: 20 pages, references adde
BFKL approach and 2->5 MHV amplitude
We study MHV amplitude for the 2 -> 5 scattering in the multi-Regge
kinematics. The Mandelstam cut correction to the BDS amplitude is calculated in
the leading logarithmic approximation (LLA) and the corresponding remainder
function is given to any loop order in a closed integral form. We show that the
LLA remainder function at two loops for 2 -> 5 amplitude can be written as a
sum of two 2 -> 4 remainder functions due to recursive properties of the
leading order impact factors. We also make some generalizations for the MHV
amplitudes with more external particles. The results of the present study are
in agreement with all leg two loop symbol derived by Caron-Huot as shown in a
parallel paper of one of the authors with collaborators.Comment: 24 pages, 17 figure
Electroweak higher-order effects and theoretical uncertainties in deep-inelastic neutrino scattering
A previous calculation of electroweak O(alpha) corrections to deep-inelastic
neutrino scattering, as e.g. measured by NuTeV and NOMAD, is supplemented by
higher-order effects. In detail, we take into account universal two-loop
effects from \Delta\alpha and \Delta\rho as well as higher-order final-state
photon radiation off muons in the structure function approach. Moreover, we
make use of the recently released O(alpha)-improved parton distributions
MRST2004QED and identify the relevant QED factorization scheme, which is DIS
like. As a technical byproduct, we describe slicing and subtraction techniques
for an efficient calculation of a new type of real corrections that are induced
by the generated photon distribution. A numerical discussion of the
higher-order effects suggests that the remaining theoretical uncertainty from
unknown electroweak corrections is dominated by non-universal two-loop effects
and is of the order 0.0003 when translated into a shift in
sin^2\theta_W=1-MW^2/MZ^2. The O(alpha) corrections implicitly included in the
parton distributions lead to a shift of about 0.0004.Comment: 25 pages, latex, 8 postscript figure
The Influence of Strong Interaction on the Pionium Wave Functions at Small Distances
The influence of strong interaction of the behaviour of pionium
nS-state wave functions at small distance are investigated both analytically
(perturbatively) and so numerically. It is shown that in the whole the
accounting of strong interaction results in multiplying of pure Coulomb pionium
wave functions by some function practically independent on value of principal
quantum number n. Due to this reason the n-independence of probability of
atom production in nS-state remains the same as in case of pure
Coulomb interactionComment: 4 pages, 2 figure
N=4 supersymmetric Yang Mills scattering amplitudes at high energies: the Regge cut contribution
We further investigate, in the planar limit of N=4 supersymmetric Yang Mills
theories,the high energy Regge behavior of six-point MHV scattering amplitudes.
In particular, for the new Regge cut contribution found in our previous paper,
we compute in the leading logarithmic approximation (LLA) the energy spectrum
of the BFKL equation in the color octet channel, and we calculate explicitly
the two loop corrections to the discontinuities of the amplitudes for the
transitions 2 to 4 and 3 to 3. We find an explicit solution of the BFKL
equation for the octet channel for arbitrary momentum transfers and investigate
the intercepts of the Regge singularities in this channel. As an important
result we find that the universal collinear and infrared singularities of the
BDS formula are not affected by this Regge-cut contribution. Any improvement of
the BDS formula should reproduce this cut to all orders in the coupling
Azimuthal decorrelation of Mueller-Navelet jets at the Tevatron and the LHC
We study the production of Mueller-Navelet jets at hadron colliders in the
Balitsky-Fadin-Kuraev-Lipatov (BFKL) framework. We show that a measurement of
the relative azimuthal angle \Delta\Phi between the jets can provide a good
testing ground for corrections due to next-leading logarithms (NLL). Besides
the well-known azimuthal decorrelation with increasing rapidity interval
\Delta\eta between the jets, we propose to also measure this effect as a
function of R=k_2/k_1, the ratio between the jets transverse momenta. Using
renormalisation-group improved NLL kernel, we obtain predictions for
d\sigma/d\Delta\eta dR d\Delta\Phi. We analyse NLL-scheme and
renormalisation-scale uncertainties, and energy-momentum conservation effects,
in order to motivate a measurement at the Tevatron and the LHC.Comment: 11 pages, 7 figures, energy conservation effects adde
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