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Author |
LHCf Collaboration (Adriani, O. et al); Faus-Golfe, A.; Velasco, J. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Measurement of zero degree single photon energy spectra for sqrt(s) = 7 TeV proton-proton collisions at LHC |
Type |
Journal Article |
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Year |
2011 |
Publication |
Physics Letters B |
Abbreviated Journal |
Phys. Lett. B |
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Volume |
703 |
Issue |
2 |
Pages |
128-134 |
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Keywords |
LHC; Ultra-high energy cosmic-ray; Hadron interaction models |
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Abstract |
In early 2010. the Large Hadron Collider forward (LHCf) experiment measured very forward neutral particle spectra in LHC proton-proton collisions. From a limited data set taken under the best beam conditions (low beam-gas background and low occurrence of pile-up events), the single photon spectra at root s = 7 TeV and pseudo-rapidity (eta) ranges from 8.81 to 8.99 and from 10.94 to infinity were obtained for the first time and are reported in this Letter. The spectra from two independent LHCf detectors are consistent with one another and serve as a cross check of the data. The photon spectra are also compared with the predictions of several hadron interaction models that are used extensively for modeling ultra-high energy cosmic-ray showers. Despite conservative estimates for the systematic errors, none of the models agree perfectly with the measurements. A notable difference is found between the data and the DPMJET 3.04 and PYTHIA 8.145 hadron interaction models above 2 TeV where the models predict higher photon yield than the data. The QGSJET II-03 model predicts overall lower photon yield than the data, especially above 2 TeV in the rapidity range 8.81 < eta < 8.99. |
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Address |
[Fukatsu, K; Itow, Y; Kawade, K; Mase, T; Masuda, K; Matsubara, Y; Mitsuka, G; Muraki, Y; Sako, T; Suzuki, K; Taki, K] Nagoya Univ, Solar Terr Environm Lab, Nagoya, Aichi 4648601, Japan, Email: sako@stelab.nagoya-u.ac.jp |
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Publisher |
Elsevier Science Bv |
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Language |
English |
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Original Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0370-2693 |
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Expedition |
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Conference |
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Notes |
WOS:000295105500005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial ![sorted by Serial field, descending order (down)](img/sort_desc.gif) |
769 |
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Author |
Marinas, C.; Vos, M. |
![find record details (via OpenURL) openurl](img/xref.gif)
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Title |
The Belle-II DEPFET pixel detector: A step forward in vertexing in the superKEKB flavour factory |
Type |
Journal Article |
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Year |
2011 |
Publication |
Nuclear Instruments & Methods in Physics Research A |
Abbreviated Journal |
Nucl. Instrum. Methods Phys. Res. A |
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Volume |
650 |
Issue |
1 |
Pages |
59-63 |
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Keywords |
SuperKEKB; Belle-II; DEPFET; Pixel detector; ASIC; Mechanics; Cooling; Resolution |
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Abstract |
An upgrade of the successful asymmetric e(+)e(-) collider in KEK (Tsukuba, Japan) is foreseen by the fall of 2013. This new Super Flavor Factory will deliver an increased instantaneous luminosity of up to L = 8 x 10(35) cm(-2) s(-1), 40 times larger than the current KEKB machine. To exploit these new conditions and provide high precision measurements of the decay vertex of the B meson systems, a new silicon vertex detector will be operated in Belle. This new detector will consist of two layers of DEPFET Active Pixel Sensors as close as possible to the interaction point. DEPFET is a field effect transistor, with an additional deep implant underneath the channel's gate, integrated on a completely depleted bulk. This technology offers detection and an in-pixel amplification stage, while keeping low the power consumption. Under these conditions, thin sensors with small pixel size and low intrinsic noise are possible. In this article, an overview of the full system will be described, including the sensor, the front-end electronics and both the mechanical and thermal proposed solutions as well as the expected performance. |
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Address |
[Marinas, C; Vos, M] CSIC UVEG, IFIC, Inst Fis Corpuscular, Valencia, Spain, Email: Carlos.Marinas.Pardo@cern.ch |
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Publisher |
Elsevier Science Bv |
Place of Publication |
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English |
Summary Language |
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ISSN |
0168-9002 |
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Expedition |
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Conference |
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Notes |
WOS:000295106500015 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ elepoucu @ |
Serial ![sorted by Serial field, descending order (down)](img/sort_desc.gif) |
768 |
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Permanent link to this record |
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Author |
Moles-Valls, R. |
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Title |
Alignment of the ATLAS Inner Detector with proton-proton collision data |
Type |
Journal Article |
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Year |
2011 |
Publication |
Nuclear Instruments & Methods in Physics Research A |
Abbreviated Journal |
Nucl. Instrum. Methods Phys. Res. A |
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Volume |
650 |
Issue |
1 |
Pages |
235-239 |
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Keywords |
ATLAS; Inner detector; Tracking system; Alignment |
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Abstract |
ATLAS is a multipurpose experiment that records the products of the LHC collisions. In order to reconstruct the trajectories of the charged particles produced in these collisions. ATLAS has an internal tracking system made of silicon planar sensors (pixels and micro-strips) and drift-tube based detectors; both together, they constitute the ATLAS Inner Detector. The alignment of the ATLAS tracking system requires the determination of their almost 36,000 degrees-of-freedom (DOF) with high accuracy. Thus, the demanded precision for the alignment of the pixel and micro-strip sensors is below 10 μm. As alignment algorithms are based on the minimization of the track-hit residuals, a linear system with a large number of DOF has to be solved. The alignment results of the ATLAS tracker using data recorded during cosmic commissioning phases in 2008 and 2009 and the LHC start up run in 2009 will be presented. Moreover recent 7 TeV data collected during 2010 run have been used to study the detector performance. These studies reveal that the detector is aligned with a precision high enough to cope with the requirements. |
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Address |
[Moles-Valls, R] IFIC CSIC UV Valencia, Valencia, Spain, Email: Regina.Moles@ific.uv.es |
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Publisher |
Elsevier Science Bv |
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English |
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ISSN |
0168-9002 |
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Notes |
WOS:000295106500050 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ elepoucu @ |
Serial ![sorted by Serial field, descending order (down)](img/sort_desc.gif) |
767 |
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Permanent link to this record |
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Author |
Bernabeu, J.; Espriu, D.; Puigdomenech, D. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Gravitational waves in the presence of a cosmological constant |
Type |
Journal Article |
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Year |
2011 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
84 |
Issue |
6 |
Pages |
063523 - 13pp |
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Keywords |
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Abstract |
We derive the effects of a nonzero cosmological constant Lambda on gravitational wave propagation in the linearized approximation of general relativity. In this approximation, we consider the situation where the metric can be written as g(mu nu) = eta(mu nu) + h(mu nu)(Lambda) + h(mu nu)(W), h(mu nu)(Lambda,W) << 1, where h(mu nu)(Lambda) is the background perturbation and h(mu nu)(W) is a modification interpretable as a gravitational wave. For Lambda not equal 0, this linearization of Einstein equations is self-consistent only in certain coordinate systems. The cosmological Friedmann-Robertson-Walker coordinates do not belong to this class and the derived linearized solutions have to be reinterpreted in a coordinate system that is homogeneous and isotropic to make contact with observations. Plane waves in the linear theory acquire modifications of order root Lambda, both in the amplitude and the phase, when considered in Friedmann-Robertson-Walker coordinates. In the linearization process for h(mu nu), we have also included terms of order O(Lambda h(mu nu)). For the background perturbation h(mu nu)(Lambda), the difference is very small, but when the term h(mu nu)(W)Lambda is retained the equations of motion can be interpreted as describing massive spin-2 particles. However, the extra degrees of freedom can be approximately gauged away, coupling to matter sources with a strength proportional to the cosmological constant itself. Finally, we discuss the viability of detecting the modifications caused by the cosmological constant on the amplitude and phase of gravitational waves. In some cases, the distortion with respect to gravitational waves propagating in Minkowski space-time is considerable. The effect of Lambda could have a detectable impact on pulsar timing arrays. |
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Address |
[Bernabeu, J] Univ Valencia, Dept Fis Teor IFIC, CSIC, E-46100 Valencia, Spain |
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Publisher |
Amer Physical Soc |
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English |
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Series Volume |
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ISSN |
1550-7998 |
ISBN |
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Conference |
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Notes |
WOS:000295223100005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ elepoucu @ |
Serial ![sorted by Serial field, descending order (down)](img/sort_desc.gif) |
766 |
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Permanent link to this record |
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Author |
Battye, R.A.; Brawn, G.D.; Pilaftsis, A. |
![goto web page (via DOI) doi](img/doi.gif)
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Title |
Vacuum topology of the two Higgs doublet model |
Type |
Journal Article |
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Year |
2011 |
Publication |
Journal of High Energy Physics |
Abbreviated Journal |
J. High Energy Phys. |
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Volume |
08 |
Issue |
8 |
Pages |
020 - 75pp |
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Keywords |
Higgs Physics; Spontaneous Symmetry Breaking; CP violation |
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Abstract |
We perform a systematic study of generic accidental Higgs-family and CP symmetries that could occur in the two-Higgs-doublet-model potential, based on a Majorana scalar-field formalism which realizes a subgroup of GL(8, C). We derive the general conditions of convexity and stability of the scalar potential and present analytical solutions for two non-zero neutral vacuum expectation values of the Higgs doublets for a typical set of six symmetries, in terms of the gauge-invariant parameters of the theory. By means of a homotopy-group analysis, we identify the topological defects associated with the spontaneous symmetry breaking of each symmetry, as well as the massless Goldstone bosons emerging from the breaking of the continuous symmetries. We find the existence of domain walls from the breaking of Z(2), CP1 and CP2 discrete symmetries, vortices in models with broken U(1)(PQ) and CP3 symmetries and a global monopole in the SO(3)(HF)-broken model. The spatial profile of the topological defect solutions is studied in detail, as functions of the potential parameters of the two-Higgs doublet model. The application of our Majorana scalar-field formalism in studying more general scalar potentials that are not constrained by the U(1)(Y) hypercharge symmetry is discussed. In particular, the same formalism may be used to properly identify seven additional symmetries that may take place in a U(1)(Y)-invariant scalar potential. |
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Address |
[Battye, RA; Brawn, GD] Univ Manchester, Jodrell Bank, Ctr Astrophys, Sch Phys & Astron, Manchester M13 9PL, Lancs, England, Email: rbattye@jb.man.ac.uk |
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Thesis |
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Publisher |
Springer |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
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Original Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1126-6708 |
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Notes |
WOS:000294901400062 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ elepoucu @ |
Serial ![sorted by Serial field, descending order (down)](img/sort_desc.gif) |
765 |
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Permanent link to this record |