Measurement of the Fermi Constant by FAST

An initial measurement of the lifetime of the positive muon to a precision of 16 parts per million (ppm) has been performed with the FAST detector at the Paul Scherrer Institute. The result is tau_mu = 2.197083 (32) (15) microsec, where the first error is statistical and the second is systematic. The muon lifetime determines the Fermi constant, G_F = 1.166353 (9) x 10^-5 GeV^-2 (8 ppm).Comment: 15 pages, 6 figure

A mobile data acquisition system

A mobile data aquisition (MobiDAQ) was developed for the ATLAS central hadronic calorimeter (TileCal). MobiDAQ has been designed in order to test the functionalities of the TileCal front-end electronics and to acquire calibration data before the final back-end electronics were built and tested. MobiDAQ was also used to record the first cosmic ray events acquired by an ATLAS subdetector in the underground experimental area

Electroweak Physics, Experimental Aspects

Collider measurements on electroweak physics are summarised. Although the precision on some observables is very high, no deviation from the Standard Model of electroweak interactions is observed. The data allow to set stringent limits on some models for new physics.Comment: Plenary Talk at the UK Phenomenology Workshop on Collider Physics, Durham, 199

Isotopic Dependence of the Nuclear Caloric Curve

The A/Z dependence of projectile fragmentation at relativistic energies has been studied with the ALADIN forward spectrometer at SIS. A stable beam of 124Sn and radioactive beams of 124La and 107Sn at 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z of the produced spectator sources, consistent with predictions for expanded systems. Small Coulomb effects (\Delta T \approx 0.6 MeV) appear for residue production near the onset of multifragmentation.Comment: 11 pages, 3 figures, accepted for publ. in Phys. Rev. Let

Tracing a phase transition with fluctuations of the largest fragment size: Statistical multifragmentation models and the ALADIN S254 data

A phase transition signature associated with cumulants of the largest fragment size distribution has been identified in statistical multifragmentation models and examined in analysis of the ALADIN S254 data on fragmentation of neutron-poor and neutron-rich projectiles. Characteristics of the transition point indicated by this signature are weakly dependent on the A/Z ratio of the fragmenting spectator source. In particular, chemical freeze-out temperatures are estimated within the range 5.9 to 6.5 MeV. The experimental results are well reproduced by the SMM model.Comment: 7 pages, 3 figures, Proceedings of the International Workshop on Multifragmentation and Related Topics (IWM2009), Catania, Italy, November 2009

Neutron recognition in the LAND detector for large neutron multiplicity

The performance of the LAND neutron detector is studied. Using an event-mixing technique based on one-neutron data obtained in the S107 experiment at the GSI laboratory, we test the efficiency of various analytic tools used to determine the multiplicity and kinematic properties of detected neutrons. A new algorithm developed recently for recognizing neutron showers from spectator decays in the ALADIN experiment S254 is described in detail. Its performance is assessed in comparison with other methods. The properties of the observed neutron events are used to estimate the detection efficiency of LAND in this experiment.Comment: 16 pages, 8 figure

Gross Properties and Isotopic Phenomena in Spectator Fragmentation

A systematic study of isotopic effects in the break-up of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory. Searching for signals of criticality in the fragment production we have applied the model independent universal fluctuations theory already proposed to track criticality signals in multifragmentation to our data. The fluctuation of the largest fragment charge and of the asymmetry of the two and three largest fragments and their bimodal distribution have also been analysed.Comment: 6 pages, 4 figures, IX International Conference on Nucleus-Nucleus Collisions, Rio de Janeiro, Brazil, August 28 - September 1, 200

Simultaneous Extraction of the Fermi constant and PMNS matrix elements in the presence of a fourth generation

Several recent studies performed on constraints of a fourth generation of quarks and leptons suffer from the ad-hoc assumption that 3 x 3 unitarity holds for the first three generations in the neutrino sector. Only under this assumption one is able to determine the Fermi constant G_F from the muon lifetime measurement with the claimed precision of G_F = 1.16637 (1) x 10^-5 GeV^-2. We study how well G_F can be extracted within the framework of four generations from leptonic and radiative mu and tau decays, as well as from K_l3 decays and leptonic decays of charged pions, and we discuss the role of lepton universality tests in this context. We emphasize that constraints on a fourth generation from quark and lepton flavour observables and from electroweak precision observables can only be obtained in a consistent way if these three sectors are considered simultaneously. In the combined fit to leptonic and radiative mu and tau decays, K_l3 decays and leptonic decays of charged pions we find a p-value of 2.6% for the fourth generation matrix element |U_{e 4}|=0 of the neutrino mixing matrix.Comment: 19 pages, 3 figures with 16 subfigures, references and text added refering to earlier related work, figures and text in discussion section added, results and conclusions unchange

Challenges in QCD matter physics --The scientific programme of the Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sNN= 2.7--4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (μB> 500 MeV), effects of chiral symmetry, and the equation of state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2024, in the context of the worldwide efforts to explore high-density QCD matter