| 1. |
- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 2. |
- Aggarwal, M. M., et al.
(författare)
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Pion freeze-out time in Pb plus Pb collisions at 158 AGeV/c studied via pi(-)/pi(+) and K-/K+ ratios
- 2006
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 48:2, s. 343-352
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the final state Coulomb interaction on particles produced in Pb + Pb collisions at 158AGeV/c has been investigated in the WA98 experiment through the study of the pi(-)/pi(+) and K-/K+ ratios measured as a function of T-m- (m)0. While the ratio for kaons shows no significant T-m dependence, the pi(-)/pi(+) ratio is enhanced at small T-m - (m)0 values with an enhancement that increases with centrality. A silicon pad detector located near the target is used to estimate the contribution of hyperon decays to the pi(-)/pi(+) ratio. The comparison of results with predictions of the RQMD model in which the Coulomb interaction has been incorporated allows to place constraints on the time of the pion freeze-out.
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| 3. |
- Aggarwal, M. M., et al.
(författare)
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Suppression of high-p(T) neutral pion production in central Pb+Pb collisions at root s(NN)=17.3 GeV relative to p+C and p+Pb collisions
- 2008
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Ingår i: Physical Review Letters. - 1079-7114. ; 100:24
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Tidskriftsartikel (refereegranskat)abstract
- Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at root s(NN) = 17.4 GeV at midrapidity (2.3 less than or similar to eta(lab)less than or similar to 3.0) over the range 0.7 less than or similar to p(T)less than or similar to 3.5 GeV/c. The spectra are compared to pi(0) spectra measured in Pb+Pb collisions at root s(NN) = 17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N-part less than or similar to 300), the yield of pi(0)'s with p(T)greater than or similar to 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N-coll), while for central Pb+Pb collisions with N-part greater than or similar to 350, the pi(0) yield is suppressed.
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| 4. |
- Aggarwal, MM, et al.
(författare)
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Event-by-event fluctuations in particle multiplicities and transverse energy produced in 158A GeVPb plus Pb collisions
- 2002
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 65:5
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Tidskriftsartikel (refereegranskat)abstract
- Event-by-event fluctuations in the multiplicities of charged particles and photons, and the total transverse energy in 158A GeV Pb+Pb collisions are studied for a wide range of centralities. For narrow centrality bins the multiplicity and transverse energy distributions are found to be near perfect Gaussians. The effect of detector acceptance on the multiplicity fluctuations has been studied and demonstrated to follow statistical considerations. The centrality dependence of the charged particle multiplicity fluctuations in the measured data has been found to agree reasonably well with those obtained from a participant model. However, for photons the multiplicity fluctuations have been found to be lower compared to those obtained from a participant model. The multiplicity and transverse energy fluctuations have also been compared to those obtained from the VENUS event generator.
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| 5. |
- Aggarwal, MM, et al.
(författare)
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Transverse mass distributions of neutral pions from Pb-208-induced reactions at 158 center dot A GeV
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 23:2, s. 225-236
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Tidskriftsartikel (refereegranskat)abstract
- Results on transverse mass spectra of neutral pious measured at central rapidity are presented for impact parameter selected 158-A GeV Pb + Pb-1 and Pb + Nb collisions. The distributions cover the range 0.5 GeV/c(2) less than or equal to MT - Mo less than or equal to 4 GeV/c(2). The change of the spectral shape and the multiplicity with centrality is studied in detail. In going from p+p to semi-peripheral Pb+Pb collisions there is a nuclear enhancement increasing with transverse mass similar to the well known Cronin effect, while for very central collisions this enhancement appears to be weaker than expected.
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| 6. |
- Aggarwal, MM, et al.
(författare)
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Centrality and transverse momentum dependence of collective flow in 158 A GeV Pb+Pb collisions measured via inclusive photons
- 2005
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 762:1-2, s. 129-146
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Tidskriftsartikel (refereegranskat)abstract
- Directed and elliptic flow of inclusive photons near mid-rapidity in 158 A GeV Pb + Pb collisions has been studied. The data have been obtained with the photon spectrometer LEDA of the WA98 experiment at the CERN SPS. The flow strength has been measured for various centralities as a function of p(T) and rapidity over 0. 18 < p(T) < 1.5 GeV/c and 2.3 < y < 2.9. The angular anisotropy has been studied relative to an event plane obtained in the target fragmentation region that shows the elliptic flow to be in-plane. The elliptic flow has also been studied using two-particle correlations and shown to give similar results. A small directed flow component is observed. Both the directed and elliptic flow strengths increase with p(T). The photon flow results are used to estimate the corresponding neutral pion flow.
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| 7. |
- Aggarwal, MM, et al.
(författare)
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Centrality dependence of charged-neutral particle fluctuations in 158A (GeVPb)-Pb-208+Pb-208 collisions
- 2003
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:4
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Tidskriftsartikel (refereegranskat)abstract
- Results on the study of localized fluctuations in the multiplicity of charged particles and photons produced in 158A GeV/c Pb+Pb collisions are presented for varying centralities. The charged versus neutral particle multiplicity correlations in common phase space regions of varying azimuthal sizes are analyzed by two different methods. Various types of mixed events are constructed to probe fluctuations arising from different sources. The measured results are compared to those from simulations and from mixed events. The comparison indicates the presence of nonstatistical fluctuations in both the charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charged-neutral fluctuations, a possible signature of formation of disoriented chiral condensates, are observed. An upper limit on the production of disoriented chiral condensates is set.
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| 8. |
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| 9. |
- Aggarwal, M M, et al.
(författare)
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Azimuthal anisotropy of photon and charged particle emission in Pb-208+Pb-208 collisions at 158 center dot A GeV/c
- 2005
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 41:3, s. 287-296
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Tidskriftsartikel (refereegranskat)abstract
- The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in Pb-208 + Pb-208 collisions at 158 (.) A GeV/c in the WA98 experiment at the CERN SPS. The anisotropy of the azimuthal distributions is characterized using a Fourier analysis. For both the photon and charged particle distributions the first two Fourier coefficients are observed to decrease with increasing centrality. The observed anisotropies of the photon distributions compare well with the expectations from the charged particle measurements for all centralities.
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| 10. |
- Kelsall, N. S., et al.
(författare)
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Testing mean-field models near the N=Z line : gamma-ray spectroscopy of the T-z=1/2 nucleus Kr-73
- 2002
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 65:4
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in the N=Z+1 nucleus Kr-73 have been investigated using the Ca-40(Ar-36,2pn) and Ca-40(Ca-40,alpha2pn) reactions at 145 and 160 MeV, respectively. gamma rays were detected using the Gammasphere array and events were recorded in coincidence with charged-particle and neutron detectors. The three previously observed bands were extended to high spin, and a new unfavored positive-parity band has been observed. The alignment characteristics and decay properties of the bands are all consistent with large-deformation prolate rotation, with no clear evidence for oblate bands or shape coexistence. This is quite different from neighboring Kr-72,Kr-74, indicating a strong shape-stabilizing role for the valence neutron. The experimental results are compared to extended total Routhian surface, cranked Nilsson Strutinsky, and cranked relativistic mean-field calculations. The results suggest that the paired calculations lack some important physics. Neutron-proton correlations may be the missing ingredient. There is also evidence for an unusual band crossing in the negative-parity bands, which may indicate the presence of T=0 pairing correlations. At high spin all the models can reproduce the experimental data.
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