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Hamburg, Germany

The Deutsches Elektronen-Synchrotron , commonly abbreviated DESY, is a national research center in Germany that operates particle accelerators used to investigate the structure of matter. It conducts a broad spectrum of inter-disciplinary scientific research in three main areas: particle and high energy physics; photon science; and the development, construction and operation of particle accelerators. DESY is publicly financed by the Federal Republic of Germany, the States of Germany, and the German Research Foundation . DESY is a member of the Helmholtz Association and operates at sites in Hamburg and Zeuthen. Wikipedia.


Wang W.,German Electron Synchrotron
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

In the framework of the soft-collinear effective theory, we demonstrate that the leading-power heavy-to-light baryonic form factors at large recoil obey the heavy quark and large energy symmetries. Symmetry breaking effects are suppressed by Λ/m b or Λ/E, where Λ is the hadronic scale, m b is the b quark mass and E~m b is the energy of light baryon in the final state. At leading order, the leading power baryonic form factor ξ Λ,p(E), in which two hard-collinear gluons are exchanged in the baryon constituents, can factorize into the soft and collinear matrix elements convoluted with a hard-kernel of order αs2. Including the energy release dependence, we derive the scaling law ξ Λ,p(E)~Λ 2/E 2. We also find that this form factor ξ Λ(E) is numerically smaller than the form factor governed by soft processes, although the latter is formally power-suppressed. © 2012 Elsevier B.V. Source


Buhler R.,German Electron Synchrotron | Blandford R.,Kavli Institute for Particle Astrophysics and Cosmology
Reports on Progress in Physics | Year: 2014

The Crab nebula and its pulsar (referred to together as 'the Crab') have historically played a central role in astrophysics. True to this legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days, were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae. © 2014 IOP Publishing Ltd. Source


Lebedev O.,German Electron Synchrotron
European Physical Journal C | Year: 2012

In the Standard Model (SM), the Higgs mass around 125 GeV implies that the electroweak vacuum is metastable since the quartic Higgs coupling turns negative at high energies. I point out that a tiny mixing of the Higgs with a heavy singlet can make the electroweak vacuum completely stable. This is due to a tree level correction to the Higgs mass-coupling relation, which survives in the zero-mixing/heavy-singlet limit. Such a situation is experimentally indistinguishable from the SM, unless the Higgs self-coupling can be measured. As a result, Higgs inflation and its variants can still be viable. © 2012 Springer-Verlag / Società Italiana di Fisica. Source


Wolf G.,German Electron Synchrotron
Reports on Progress in Physics | Year: 2010

The electron-proton collider HERA at DESY opened the door for the study of diffraction in real and virtual photon-proton scattering at centre-of-mass energies W up to 250 GeV and for large negative mass squared -Q2 of the virtual photon up to Q2 = 1600 GeV2. At W = 220 GeV and Q 2 = 4 GeV2, diffraction accounts for about 15% of the total virtual photon-proton cross section, decreasing to ≈5% at Q2 = 200 GeV2. An overview of the results obtained by the experiments H1 and ZEUS on the production of neutral vector mesons and on inclusive diffraction up to the year 2008 is presented. © 2010 IOP Publishing Ltd. Source


A method to provide absolute planarity measurements through an interferometric oblique incidence setup and an iterative algorithm is presented. With only three measurements, the calibration of absolute planarity is achieved in a fast and effective manner. Demonstration with synthetic data is provided, and the possible application to very long flat mirrors is pointed out. © 2014 Optical Society of America. Source

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