Charge correlations as a probe of nuclear disassembly

SIGLEAvailable from TIB Hannover: RO 801(92-23) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Breakup configurations in multiple disintegration of projectile fragments

Kinematic correlations between three heavy projectile fragments produced in Au induced reactions at E/A=600 MeV are presented. The sensitivity of these correlations to the disassembly geometry is confirmed by classical three-body trajectory calculations. The simulations suggest a fast disintegration process of an highly excited system. Within the assumed scenarios the data constrain a possibly existing radial flow to a maximum value of about 1 MeV per nucleon. This radial motion can be provided by the Coulomb repulsion between the fragments if the breakup occurs out of a volume with a radius not larger than 15 fm. (orig.)SIGLEAvailable from TIB Hannover: RO 801(93-54) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Multifragmentation in peripheral nucleus-nucleus collisions

The complete fragmentation of highly excited nuclear systems into fragments of intermediate mass is observed in heavy-ion reactions at relativistic bombarding energies in the range of several hundreds of MeV per nucleon. Similar features are found for peripheral collisions between heavy nuclei and for more central collisions between a heavy and a light nucleus. The partition space explored in multifragment decays is well described by the statistical multifragmentation models. The expansion before breakup is confirmed by the analysis of the measured fragment energies of ternary events in their own rest frame. Collective radial flow is confined to rather small values in these peripheral-type reactions. Many conceptually different models seem to be capable of reproducing the charge correlations measured for the multifragment decays. (orig.)Available from TIB Hannover: RO 801(93-76) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

QMD simulation of multifragment production in heavy ion collisions at E/A=600 MeV

With the ALADIN forward spectrometer the fragmentation of gold nuclei at 600 MeV per nucleon after interaction with carbon, aluminum, copper and lead targets has been investigated. The results are compared to quantum-molecular-dynamics calculations using soft and hard equations of state as well as soft equation of state with momentum dependent forces. Whereas the QMD has been successfully applied to heavy ion collisions at lower energies, it is not possible to reproduce the fragment distributions and the light particle multiplicities observed in this experiment at relativistic energies. To study the reasons for the discrepancy between the experimental data and the simulations, we investigated the time evolution of the nuclear system after a collision and the disintegration pattern of excited nuclei in the QMD approach. (orig.)SIGLEAvailable from TIB Hannover: RO 801(93-29) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Statistical fragmentation of Au projectiles at E/A=600 MeV

SIGLEAvailable from TIB Hannover: RO 801(92-17) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Fragment flow and the multifragmentation phase space

Fragment distributions have been measured for Au + Au collisions at E/A 100 MeV and 1000 MeV. A high detection efficiency for fragments in nearly 4#pi# geometry was obtained by combining the Aladin forward spectrometer system and the MSU-Miniball/WU-Miniwall array. At both energies the maximum multiplicity of intermediate mass fragments normalized to the size of the decaying system is about one IMF per 30 nucleons but the element distributions show significant differences. Within a coalescence picture the suppression of heavy fragments in central collisions at E/A = 100 MeV may be related to a reduction of the density in momentum space which is caused by the collective expansion velocity component. (orig.)Available from TIB Hannover: RO 801(94-46) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Universality of spectator fragmentation at relativistic bombarding energies

Multi-fragment decays of "1"2"9Xe, "1"9"7Au, and "2"3"8U projectiles in collisions with Be, C, Al, Cu, In, Au, and U targets at energies between E/A=400 MeV and 1000 MeV have been studied with the ALADIN forward-spectrometer at SIS. By adding an array of 84 Si-CsI(Tl) telescopes the solid-angle coverage of the setup was extended to #theta#_l_a_b=16 . This permitted the complete detection of fragments from the projectile-spectator source. The dominant feature of the systematic set of data is the Z_b_o_u_n_d universality that is obeyed by the fragment multiplicities and correlations. These observables are invariant with respect to the entrance channel if plotted as a function of Z_b_o_u_n_d, where Z_b_o_u_n_d is the sum of the atomic numbers Z_i of all projectile fragments with Z_i#>=#2. No significant dependence on the bombarding energy nor on the target mass is observed. The dependence of the fragment multiplicity on the projectile mass follows a linear scaling law. The reasons for and the limits of the observed universality of spectator fragmentation are explored within the realm of the available data and with model studies. It is found that the universal properties should persist up to much higher bombarding energies than explored in this work and that they are consistent with universal features exhibited by the intranuclear cascade and statistical multifragmentation models. (orig.)Available from TIB Hannover: RO 801(96-26) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Search for a standard model-like Higgs boson in the mu(+)mu(-) and e(+)e(-) decay channels at the LHC

A search is presented for a standard model-like Higgs boson decaying to the mu(+)mu(-) or e(+)e(-) final states based on proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to integrated luminosities of 5.0 fb(-1) at a centre-of-mass energy of 7 TeV and 19.7 fb(-1) at 8 TeV for the mu(+)mu(-) search, and of 19.7 fb(-1) at 8 TeV for the e(+)e(-) search. Upper limits on the production cross section times branching fraction at the 95% confidence level are reported for Higgs boson masses in the range from 120 to 150 GeV. For a Higgs boson with a mass of 125 GeV decaying to mu(+)mu(-), the observed (expected) upper limit on the production rate is found to be 7.4 (6.5(-1.9)(+2.8)) times the standard model value. This corresponds to an upper limit on the branching fraction of 0.0016. Similarly, for e(+)e(-), an upper limit of 0.0019 is placed on the branching fraction, which is approximate to 3.7 x 10(5) times the standard model value. These results, together with recent evidence of the 125 GeV boson coupling to tau-leptons with a larger branching fraction consistent with the standard model, confirm that the leptonic couplings of the new boson are not flavour-universal

Koulutusluokitus : Koulutuskoodimuutokset vuonna 1989, Liite 3

A measurement of inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton-proton collisions at $\sqrt{s}$ = 8 TeV are presented. A data sample, corresponding to an integrated luminosity of 19.6 inverse-femtobarns was collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes $ZZ \to lll'l'$, where $l = e, \mu$ and $l' = e, \mu, \tau$. The measured total cross section, $\sigma (pp \to ZZ) = 7.7 \pm 0.5 (stat.)^{+0.5}_{-0.4} (syst.) \pm 0.4 (theo.) \pm 0.2 (lum.) pb$ for both Z bosons produced in the mass range $m_Z$ within 60 and 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ$\gamma$ couplings at the 95% confidence level: $f_4^Z$ in (-0.004,+0.004), $f_5^Z$ in (-0.005,+0.005), $f_4^\gamma$ in (-0.004,+0.004), and $f_5^\gamma$ in (-0.005,+0.005)