Diseño de un entorno para el estudio de los parámetros de funcionamiento del protocolo TCP

El protocol TCP pot veure reduïdes les seves prestacions quan la xarxa que el suporta correspon a una xarxa sense fils i amb molts errors de transmissió. Per solucionar aquest problema i adaptar millor aquest protocol a entorns més ostils s'han proposat solucions diverses que van des de la configuració adequada dels paràmetres de funcionament del protocol fins a protostes de TCPs modificats amb mecanismes adaptats a l'entorn que el suporta. L'objectiu del projecte és estudiar i desenvolupar un entorn d'avaluació basat en el simulador NS que permeti i faciliti l'estudi de les prestacions del TCP a partir de la modificació dels seus paràmetres. El projecte constarà de les següents fases: - Estudi del mòdul TCP del simulador NS - Especificació dels paràmetres a estudiar - Desenvolupament de l'entorn de simulació sobre NS - Avaluació del TCP per a paràmetres mostra i comprovació dels resultats - Conclusion

Search for composite and exotic fermions at LEP2

A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172 GeV and 161 GeV. The search for pair-produced new leptons establishes 95% confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermion

Search for promptly produced heavy quarkonium states in hadronic Z decays

A search has been made for direct production of heavy quarkonium states in more than 3 million hadronicZ 0 decays in the 1991¿1994 DELPHI data. PromptJ/ψ, ψ(2S) andΓ candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay vertex positions. New upper limits are set at the 90% confidence level forBr(Z 0→(Qq)X)/Br(Z 0→ hadrons) for various strong production mechanisms ofJ/ψ andΓ; these range down to 0.9×10−4. The limits are set in the presence of a small excess (∼1% statistical probability of a background fluctuation) in the sum of candidates from promptJ/ψ, ψ(2S),γ(1S),γ(2S) andγ(3S) relative to the estimated background

Measurement of the gluon fragmentation function and a comparison of the scaling violation in gluon and quarks jets

The fragmentation functions of quarks and gluons are measured in various three-jet topologies in Z decays from the full data set collected with the Delphi detector at the Z resonance between 1992 and 1995. The results at different values of transverse momentum-like scales are compared. A parameterization of the quark and gluon fragmentation functions at a fixed reference scale is given. The quark and gluon fragmentation functions show the predicted pattern of scaling violations. The scaling violation for quark jets as a function of a transverse momentum-like scale is in a good agreement with that observed in lower energy e+e− annihilation experiments. For gluon jets it appears to be significantly stronger. The scale dependences of the gluon and quark fragmentation functions agree with the prediction of the DGLAP evolution equations from which the colour factor ratio CA/CF is measured to be: CACF=2.26±0.09stat.±0.06sys.±0.12clus.,scale

Investigation of the splitting of quark and gluon jets

The splitting processes in identified quark and gluon jets are investigated using longitudinal and transverse observables. The jets are selected from symmetric three-jet events measured in Z decays with the Delphi detector in 1991-1994. Gluon jets are identified using heavy quark anti-tagging. Scaling violations in identified gluon jets are observed for the first time. The scale energy dependence of the gluon fragmentation function is found to be about two times larger than for the corresponding quark jets, consistent with the QCD expectation TeX . The primary splitting of gluons and quarks into subjets agrees with fragmentation models and, for specific regions of the jet resolution TeX , with NLLA calculations. The maximum of the ratio of the primary subjet splittings in quark and gluon jets is TeX . Due to non-perturbative effects, the data are below the expectation at small TeX . The transition from the perturbative to the non-perturbative domain appears at smaller TeX for quark jets than for gluon jets. Combined with the observed behaviour of the higher rank splittings, this explains the relatively small multiplicity ratio between gluon and quark jets

Diseño de un entorno para el estudio de los parámetros de funcionamiento del protocolo TCP

El protocol TCP pot veure reduïdes les seves prestacions quan la xarxa que el suporta correspon a una xarxa sense fils i amb molts errors de transmissió. Per solucionar aquest problema i adaptar millor aquest protocol a entorns més ostils s'han proposat solucions diverses que van des de la configuració adequada dels paràmetres de funcionament del protocol fins a protostes de TCPs modificats amb mecanismes adaptats a l'entorn que el suporta. L'objectiu del projecte és estudiar i desenvolupar un entorn d'avaluació basat en el simulador NS que permeti i faciliti l'estudi de les prestacions del TCP a partir de la modificació dels seus paràmetres. El projecte constarà de les següents fases: - Estudi del mòdul TCP del simulador NS - Especificació dels paràmetres a estudiar - Desenvolupament de l'entorn de simulació sobre NS - Avaluació del TCP per a paràmetres mostra i comprovació dels resultats - Conclusion

Diseño de un entorno para el estudio de los parámetros de funcionamiento del protocolo TCP

El protocol TCP pot veure reduïdes les seves prestacions quan la xarxa que el suporta correspon a una xarxa sense fils i amb molts errors de transmissió. Per solucionar aquest problema i adaptar millor aquest protocol a entorns més ostils s'han proposat solucions diverses que van des de la configuració adequada dels paràmetres de funcionament del protocol fins a protostes de TCPs modificats amb mecanismes adaptats a l'entorn que el suporta.L'objectiu del projecte és estudiar i desenvolupar un entorn d'avaluació basat en el simulador NS que permeti i faciliti l'estudi de les prestacions del TCP a partir de la modificació dels seus paràmetres. El projecte constarà de les següents fases:- Estudi del mòdul TCP del simulador NS- Especificació dels paràmetres a estudiar- Desenvolupament de l'entorn de simulació sobre NS- Avaluació del TCP per a paràmetres mostra i comprovació dels resultats- Conclusion

Search for charginos, neutralinos and gravitinos at LEP

Abreu, P. et al.An update of the searches for charginos and neutralinos in DELPHI is presented, based mainly on recent data collected at centre-of-mass energies of 161 GeV and 172 GeV. No signal is found. For a sneutrino with mass above 300 GeV/c 2 and a mass difference between the chargino and the lightest neutralino above 10 GeV/c 2, the lower limit at 95% confidence level on the chargino mass ranges from 84.3 GeV/c 2 to the kinematical limit (86.0 GeV/c 2), depending on the mixing parameters. The limit decreases for lower chargino-neutralino mass differences. The limit in the case of a light sneutrino is 67.6 GeV/c 2, provided that that there is no light sneutrino with a mass within 10 GeV/c 2 below the chargino mass. Upper limits on neutralino pair production cross-sections of about a picobarn are derived. The (μ,M 2) domain excluded in the MSSM-GUT scenario is determined by combining the neutralino and chargino searches. These results imply a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 24.9 GeV/c 2 for tanß >- 1. The search has also been extended to the case where the lightest neutralino is unstable and decays into a photon and a gravitino. imply a limit on the mass of the lightest neutralino which, for a heavy sneutrino, is constrained to be above 24.9 GeV/c 2 for tanß >- 1. The search has also been extended to the case where the lightest neutralino is unstable and decays into a photon and a gravitino.We are greatly indebted to our technical collaborators and to the funding agencies for their support in building and operating the DELPHI detector.Peer reviewe

A measurement of the photon structure function F-2(gamma) at an average Q(2) of 12 GeV2/c(4)

The hadronic photon structure functionF 2 γ has been measured in theQ 2 range from 4 to 30 GeV2/c 4 and down tox values of order 0.001, using data taken with the DELPHI detector at LEP between 1991 and 1993. A comparison is made with severalF 2 γ parameterizations with special emphasis on their lowx behaviour. A result on theQ 2 evolution ofF 2 γ is presented

Determination of the e(+)e(-)->gamma gamma(gamma) cross-section at centre-of-mass energies ranging from 189 GeV to 202 GeV

A test of the QED process e+e- -> gamma gamma (gamma) is reported. The data analysed were collected with the DELPHI detector in 1998 and 1999 at the highest energies achieved at LEP, reaching 202 GeV in the centre-of-mass. The total integrated luminosity amounts to 375.7 pb^{-1}. The differential and total cross-sections for the process e+e- -> gamma gamma were measured, and found to be in agreement with the QED prediction. 95% Confidence Level (C.L.) lower limits on the QED cut-off parameters of Lambda+ > 330 GeV and Lambda- > 320 GeV were derived. A 95% C.L. lower bound on the mass of an excited electron of 311 GeV/c^2 (for lambda_gamma = 1) was obtained. s-channel virtual graviton exchange was searched for, resulting in 95% C.L. lower limits on the string mass scale, M_S: M_S > 713 GeV/c^2 (lambda = 1) and M_S > 691 GeV/c^2 (lambda = -1)