F. Matorras

Searches for invisibly decaying Higgs bosons with the DELPHI detector at LEP

Abstract.Searches for HZ production with the Higgs boson decaying into an invisible final state were performed using the data collected by the DELPHI experiment at centre-of-mass energies between 188 GeV and 209 GeV. Both hadronic and leptonic final states of the Z boson were analysed. In addition to the search for a heavy Higgs boson, a dedicated search for a light Higgs boson down to 40 GeV/c2 was performed. No signal was found. Assuming the Standard Model HZ production cross-section, the mass limit for invisibly decaying Higgs bosons is 112.1 GeV/c2 at 95% confidence level. An interpretation in the Minimal Supersymmetric extension of the Standard Model (MSSM) and in a Majoron model is also given.

Decline in Human Fertility Rates with Male Age: A Consequence of a Decrease in Male Fecundity with Aging?

Background: The objective of this study is to investigate the influence of male age on human fertility, defined as the birth rate for a given population. Methods: Data from the Spanish National Statistics Institute (INE) for the year 2004 from a total of 454,753 newborn infants and sorted by male and female age groups were evaluated. In order to correct the influence of female age-related fertility, a different analysis was performed considering only women under 30 years of age. Results: From a demographic point of view, male fertility started to decline at 35–39 years of age. This decline is constant and follows an exponential pattern (slope –0.11 to –0.12). The trend persisted when the data were adjusted for every 1,000 men in the age group, as well as when only women under the age of 30 were considered. Male fertility showed a 21–23% annual decrease starting at the age of 39. Conclusion: An exponential decrease in human fertility which is independent of the woman’s age was observed with male aging. This decay is probably due to a downfall in male fecundity, closely related to a decline in sperm quality. However, social or behavioral causes for this trend cannot be excluded.

Results on photon and neutron irradiation of semitransparent amorphous-silicon sensors

Abstract Semitransparent amorphous-silicon sensors are basic elements for laser 2D position reconstruction in the CMS multipoint alignment link system. Some of the sensors have to work in a very hard radiation environment. Two different sensor types have been irradiated with 60Co photons (up to 100 kGy) and fast neutrons (up to 10 15 cm −2 ), and the subsequent change in their performance has been measured.

Study of Z Boson Production in PbPb Collisions at √sNN=2.76 TeV

A search for Z bosons in the μ+μ− decay channel has been performed in PbPb collisions at √ sNN = 2.76 TeV with the CMS detector at the LHC, in a 7.2 μb−1 data sample. The number of opposite-sign muon pairs observed in the 60–120 GeV/c2 invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of (33.8± 5.5(stat) ± 4.4(syst)) × 10−8, in the |y| < 2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions. Submitted to Physical Review Letters ∗See Appendix A for the list of collaboration members ar X iv :1 10 2. 54 35 v1 [ nu cl -e x] 2 6 Fe b 20 11A search for Z bosons in the μ(+)μ(-) decay channel has been performed in PbPb collisions at √S(NN)=2.76  TeV with the CMS detector at the LHC, in a 7.2 μb(-1) data sample. The number of opposite-sign muon pairs observed in the 60-120 GeV/c(2) invariant mass range is 39, corresponding to a yield per unit of rapidity (y) and per minimum bias event of [33.8±5.5(stat)±4.4(syst)]×10(-8), in the |y|<2.0 range. Rapidity, transverse momentum, and centrality dependencies are also measured. The results agree with next-to-leading order QCD calculations, scaled by the number of incoherent nucleon-nucleon collisions.

Measurement of the τ topological branching ratios

Abstract Using data collected in the DELPHI detector at LEP-1, measurements of the inclusive τ branching ratios for decay modes containing one, three, or five charged particles have been performed: where h is either a charged π or K meson. The first quoted uncertainties are statistical and the second systematic.

Study of CMOS image sensors for laser beam position detection

We report on the study made on commercial CMOS image sensors in order to determine their feasibility for light beam position reconstruction. Measurements of the intrinsic position resolution, sensor photoresponse and uniformity were done. The effect of eventual background illumination was evaluated. The precision on the spatial point reconstruction was determined from linearity measurements. First results on gamma-ray radiation tolerance are presented.

Enlarged linearity range of a Rasnik system using an integrating sphere

Abstract Rasniks elements are foreseen to be used in the CMS alignment system. The large displacements and deformations expected for the different subdetectors demands large linearity response range of the alignment components. By the use of an integrating sphere coupled to the light source, we have optimized the homogenity of the beam, leading to improvement, by factor three, in the linearity range of the Rasnik system with respect to conventional configurations, preserving the measurement position resolution. The range obtained coincides with the maximum reachable with the geometry of the used components.

τ physics at LEP

Abstract This paper gives an overview of some of the more interesting results obtained at LEP in τ physics: precision measurements in neutral and charged currents universality and structure, τ mass, topological and exclusive Branching Ratios.

Gamma irradiation of semitransparent amorphous silicon sensors

Abstract Semitransparent amorphous silicon sensors are the key elements for laser light 2D position reconstruction in the CMS alignment system. Some of them have to work in very extreme radiation environment. We have irradiated with gammas, up to 10 MRad, two different sensors and measured their change in performance.

Search for charged Higgs bosons in e(+)e(-) collisions at DELPHI

A search for pair produced charged Higgs bosons was performed using the data collected by the DELPHI detector at LEP II at centre-of-mass energies up to 208 GeV. The three different final states, τντν, csτν and cscs were considered. No excess of data compared to the expected Standard Model processes was observed and the existence of a charged Higgs boson with mass lower than 75.0 GeV/c2 has been excluded at 95% confidence level.