274 research outputs found
Search for stop production in R-parity-violating supersymmetry at HERA
No full textA search for stop production in R-parity-violating supersymmetry has been performed in e+p interactions with the ZEUS detector at HERA, using an integrated luminosity of 65 pb-1. At HERA, the R-parity-violating coupling λ' allows resonant squark production, e+d→̃ q. Since the lowest-mass squark state in most supersymmetry models is the light stop, ̃t, this search concentrated on production of ̃t, followed either by a direct R-parity-violating decay, or by the gauge decay to b̃x1+. No evidence for stop production was found and limits were set on λ'131 as a function of the stop mass in the framework of the minimal supersymmetric standard model. The results have also been interpreted in terms of constraints on the parameters of the minimal supergravity model. © Springer-Verlag Berlin Heidelberg 2007
Inclusive (KSKS0)-K-0 resonance production in ep collisions at HERA
No full textInclusive (KSKS0)-K-0 production in ep collisions at the DESY ep collider HERA was studied with the ZEUS detector using an integrated luminosity of 0.5 fb(-1). Enhancements in the mass spectrum were observed and are attributed to the production of f(2)(1270)/a(2)(0)(1320), f(2)(')(1525) and f(0)(1710). Masses and widths were obtained using a fit which takes into account theoretical predictions based on SU(3) symmetry arguments, and are consistent with the Particle Data Group values. The f(0)(1710) state, which has a mass consistent with a glueball candidate, was observed with a statistical significance of 5 standard deviations. However, if this state is the same as that seen in gamma gamma -> (KSKS0)-K-0, it is unlikely to be a pure glueball state
Measurement of the cross-section ratio in exclusive photoproduction at HERA
No full textThe exclusive photoproduction reactions and
have been measured at an centre-of-mass energy
of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 373
pb. The measurement was made in the kinematic range GeV,
GeV and GeV, where is the photon--proton
centre-of-mass energy, is the photon virtuality and is the squared
four-momentum transfer at the proton vertex. The decay channels used were
, and with subsequent decay . The
ratio of the production cross sections, , has been measured as a function of and and
compared to previous data in photoproduction and deep inelastic scattering and
with predictions of QCD-inspired models of exclusive vector-meson production,
which are in reasonable agreement with the data.Comment: 31 pages, 9 figures. Updated according to comments from journal
referee including a new table. Added full collaboration author lis
FINANCIAL BUBBLE FORMATION AT THE GROWTH STAGE OF AN ECONOMIC SYSTEM
No full textThe paper studies the links between the financial bubble phenomenon manifested by the irrational growth of stock indices and development stages of Kondratiev long waves followed by the investigation of Glazyev technological patterns. The relevance of the paper is predetermined by the predicted transition of the global economy to the growth phase after the end of the current crisis, the new round of education and the deflation of financial bubbles.. The stable trends in the origination and development of financial bubbles within the long wave growth phase are described by an example of the US economy. With the use of economic statistics, the financial bubbles most typical for the growth phase are determined and the reasons for their formation are described. The case study of the US aircraft industry reveals divergent trends in the value of shares of the largest US aircraft maker Boeing and the total factor performance over the industry. On this basis, a time lag is set between the decline in the total performance factors of the 4-th pattern technologies (aircraft making) and the value of shares at the beginning of the 5-th pattern, which proves the supposed presence of a financial bubble. An attempt is made to identify financial bubbles specific for the economic growth phase within the long-wave development. Based on works of C. Perez,Soete and V. E. Dementiev, a retrospective analysis of the US economy so far as relevant to the definition of the periods and reasons for the financial bubble formation is made. The life cycle of an institutional financial bubble is analyzed and a bubble formation diagram in the growth phase is presented. Based on the hypothetic time of the final establishment of the general picture of mainstream technologies, the periodization of the sixth technological pattern stages is forecasted, which can be helpful in the development of the state R&D and innovation policy
Study of the effective transverse momentum of partons in the proton using prompt photons in photoproduction at HERA
No full textThe photoproduction of prompt photons, together with an accompanying jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb/sup -1/. A study of the effective transverse momentum, (k/sub T/), of partons in the proton, as modelled within the framework of the PYTHIA Monte Carlo, gives a value of (k/sub T/)=1.69+or-0.18/sub -0.20//sup +0.18/ GeV for the gamma p centre-of-mass energy range 134 lt W lt 251 GeV. This result is in agreement with the previously observed trend in hadron-hadron scattering for (k/sub T/) to rise with interaction energy
ФОРМИРОВАНИЕ ФИНАНСОВЫХ ПУЗЫРЕЙ НА СТАДИИ РОСТА ЭКОНОМИЧЕСКОЙ СИСТЕМЫ
No full textThe paper studies the links between the financial bubble phenomenon manifested by the irrational growth of stock indices and development stages of Kondratiev long waves followed by the investigation of Glazyev technological patterns. The relevance of the paper is predetermined by the predicted transition of the global economy to the growth phase after the end of the current crisis, the new round of education and the deflation of financial bubbles.. The stable trends in the origination and development of financial bubbles within the long wave growth phase are described by an example of the US economy. With the use of economic statistics, the financial bubbles most typical for the growth phase are determined and the reasons for their formation are described. The case study of the US aircraft industry reveals divergent trends in the value of shares of the largest US aircraft maker Boeing and the total factor performance over the industry. On this basis, a time lag is set between the decline in the total performance factors of the 4-th pattern technologies (aircraft making) and the value of shares at the beginning of the 5-th pattern, which proves the supposed presence of a financial bubble. An attempt is made to identify financial bubbles specific for the economic growth phase within the long-wave development. Based on works of C. Perez,Soete and V. E. Dementiev, a retrospective analysis of the US economy so far as relevant to the definition of the periods and reasons for the financial bubble formation is made. The life cycle of an institutional financial bubble is analyzed and a bubble formation diagram in the growth phase is presented. Based on the hypothetic time of the final establishment of the general picture of mainstream technologies, the periodization of the sixth technological pattern stages is forecasted, which can be helpful in the development of the state R&D and innovation policy
The azimuthal correlation between the leading jet and the scattered lepton in deep inelastic scattering at HERA
No full textThe azimuthal correlation angle, Δϕ, between the scattered lepton and the leading jet in deep inelastic e±p scattering at HERA has been studied using data collected with the ZEUS detector at a centre-of-mass energy of s=318GeV, corresponding to an integrated luminosity of 326pb-1. A measurement of jet cross sections in the laboratory frame was made in a fiducial region corresponding to photon virtuality 10GeV210GeV, lepton polar angle 140∘<θe<180∘, jet transverse momentum 2.5GeV<pT,jet<30GeV, and jet pseudorapidity -1.5<ηjet<1.8. Jets were reconstructed using the kT algorithm with the radius parameter R=1. The leading jet in an event is defined as the jet that carries the highest pT,jet. Differential cross sections, dσ/dΔϕ, were measured as a function of the azimuthal correlation angle in various ranges of leading-jet transverse momentum, photon virtuality and jet multiplicity. Perturbative calculations at O(αs2) accuracy successfully describe the data within the fiducial region, although a lower level of agreement is observed near Δϕ→π for events with high jet multiplicity, due to limitations of the perturbative approach in describing soft phenomena in QCD. The data are equally well described by Monte Carlo predictions that supplement leading-order matrix elements with parton showering
Jet-radius dependence of inclusive-jet cross sections in deep inelastic scattering at HERA
No full textDifferential inclusive-jet cross sections have been measured for different jet radii in neutral current deep inelastic ep scattering for boson virtualities Q2 > 125 GeV2 with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb-1. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally inclusive mode for different values of the jet radius R. Differential cross sections are presented as functions of Q2 and the jet transverse energy, ET, Bjet. The dependence on R of the inclusive-jet cross section has been measured for Q2 > 125 and 500 GeV2 and found to be linear with R in the range studied. Next-to-leading-order QCD calculations give a good description of the measurements for 0.5 ≤ R ≤ 1. A value of αs (MZ) has been extracted from the measurements of the inclusive-jet cross section d σ / d Q2 with R = 1 for Q2 > 500 GeV2: αs (MZ) = 0.1207 ± 0.0014 (stat .)-0.0033+0.0035 (exp .)-0.0023+0.0022 (th .). The variation of αs with ET, Bjet is in a good agreement with the running of αs as predicted by QCD. © 2007 Elsevier B.V. All rights reserved
Impact of jet-production data on the next-to-next-to-leading-order determination of HERAPDF2.0 parton distributions
No full textAbstract
The HERAPDF2.0 ensemble of parton distribution functions (PDFs) was introduced in 2015. The final stage is presented, a next-to-next-to-leading-order (NNLO) analysis of the HERA data on inclusive deep inelastic ep scattering together with jet data as published by the H1 and ZEUS collaborations. A perturbative QCD fit, simultaneously of
α
s
(
M
Z
2
)
and the PDFs, was performed with the result
α
s
(
M
Z
2
)
=
0.1156
±
0.0011
(
exp
)
-
0.0002
+
0.0001
(
model
+
parameterisation
)
±
0.0029
(
scale
)
. The PDF sets of HERAPDF2.0Jets NNLO were determined with separate fits using two fixed values of
α
s
(
M
Z
2
)
,
α
s
(
M
Z
2
)
=
0.1155
and 0.118, since the latter value was already chosen for the published HERAPDF2.0 NNLO analysis based on HERA inclusive DIS data only. The different sets of PDFs are presented, evaluated and compared. The consistency of the PDFs determined with and without the jet data demonstrates the consistency of HERA inclusive and jet-production cross-section data. The inclusion of the jet data reduced the uncertainty on the gluon PDF. Predictions based on the PDFs of HERAPDF2.0Jets NNLO give an excellent description of the jet-production data used as input
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