U. Amaldi

Publications (66)66.57 Total impact

• Article: 40th Anniversary of the First Proton-Proton Collisions in the CERN Intersecting Storage Rings (ISR)

  U. Amaldi, P. J. Bryant, P. Darriulat, K. Hubner
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  ABSTRACT: No Abstract of this Colloquium
  06/2012;
• Article: High-power test results of a 3 GHz single-cell cavity

  U. Amaldi, D. Bergesio, R. Bonomi, A. Degiovanni, M. Garlasché, P. Magagnin, S. Verdú-Andrés, R. Wegner
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  ABSTRACT: Compact, reliable and little consuming accelerators are required for the treatment of tumours with ions. TERA proposes the "cyclinac", composed of a high-frequency, fast-cycling linac which boosts the energy of the particles previously accelerated in a cyclotron. The dimensions of the linac can be reduced if high gradients are used. TERA initiated a high-gradient test program to understand the operational limit of such structures. The program foresees the design, prototyping and high-power test of several high-gradient structures operating at 3 and 5.7 GHz. The high-power tests of the 3 GHz single-cell cavity were completed in Winter 2012. The maximum BDR threshold measured for Emax of 170 MV/m and RF pulses of 2.5 \mu s was 3 x 10-6 bpp/m.
  06/2012;
• Article: Present challenges in hadrontherapy techniques

  U. Amaldi, S. Braccini
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  ABSTRACT: Hadrontherapy is a high-precision technique in cancer radiation therapy, which allows obtaining a superior conformal treatment with respect to photons used in conventional radiation therapy. To reach this ambitious goal without reducing the patient throughput needed in a hospital-based environment, the physical and radiobiological properties of charged hadrons, protons and carbon ions in particular, have to be exploited at best, making use of the most modern technologies issued from research in nuclear and particle physics. In the present days, we are assisting to a continuous technological challenge, leading to the conception and to the development of innovative methods and instruments. In this paper, the most relevant challenges in dose delivery systems, gantries, imaging, quality assurance and particle accelerators are reviewed.
  European Physical Journal Plus 04/2012; 126(7):1-15.
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  Available from: Jiri Masik

  Article: A study of production in e+e− collisions at –207 GeV

  DELPHI Collaboration, J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, [......], M. Winter, M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan
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  ABSTRACT: Measurements are presented of R b, the ratio of the b[`(b)]{\mathrm{b}}\bar{\mathrm{b}} cross-section to the q[`(q)]{\mathrm{q}}\bar{\mathrm{q}} cross-section in e+e− collisions, and the forward-backward asymmetry A FBb at twelve energy points in the range Ös=130\sqrt{s}=130 –207GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions.
  European Physical Journal C 04/2012; 60(1):1-15. · 3.63 Impact Factor
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  Available from: Pier Giorgio Rancoita

  Article: Search for neutral MSSM Higgs bosons at LEP

  S. Schael, R. Barate, R. Brunelière, I. De Bonis, D. Decamp, C. Goy, S. Jézéquel, J.-P. Lees, F. Martin, E. Merle, [......], G.W. Wilson, J.A. Wilson, T.R. Wyatt, S. Yamashita, D. Zer-Zion, L. Zivkovic, S. Heinemeyer, A. Pilaftsis, G. Weiglein, The LEP Working Group for Higgs Boson Searches
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  ABSTRACT: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric standard model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses of neutral Higgs bosons.
  European Physical Journal C 04/2012; 47(3):547-587. · 3.63 Impact Factor
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  Available from: Jiri Masik

  Article: Search for single top quark production via contact interactions at LEP2

  The DELPHI Collaboration, J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, [......], M. Winter, M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan
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  ABSTRACT: Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1pb−1. No evidence for a signal was found. Limits on the energy scale Λ, were set for scalar-, vector- and tensor-like coupling scenarios.
  European Physical Journal C 04/2012; 71(2):1-13. · 3.63 Impact Factor
• Article: Measurements of CP-conserving trilinear gauge boson couplings WWV (V≡γ,Z) in e+e− collisions at LEP2

  The DELPHI Collaboration, J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, [......], M. Winter, M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan
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  ABSTRACT: The data taken by Delphi at centre-of-mass energies between 189and 209GeV are used to place limits on the CP-conserving trilinear gauge boson couplings DgZ1\Delta g^{Z}_{1}, λ γ and Δκ γ associated to W + W − and single W production at Lep2. Using data from the jj ℓ ν, jjjj, jjX and ℓ X final states, where j, ℓ and X represent a jet, a lepton and missing four-momentum, respectively, the following limits are set on the couplings when one parameter is allowed to vary and the others are set to their Standard Model values of zero: ${l}\Delta g^Z_1=-0.025^{+0.033}_{-0.030},\\\noalign{\vskip6pt}\lambda_\gamma =0.002^{+0.035}_{-0.035}\qquad\mbox{and}\\\noalign{\vskip6pt}\Delta\kappa_\gamma =0.024^{+0.077}_{-0.081}.$\begin{array}{l}\Delta g^Z_1=-0.025^{+0.033}_{-0.030},\\\noalign{\vskip6pt}\lambda_\gamma =0.002^{+0.035}_{-0.035}\qquad\mbox{and}\\\noalign{\vskip6pt}\Delta\kappa_\gamma =0.024^{+0.077}_{-0.081}.\end{array} Results are also presented when two or three parameters are allowed to vary. All observations are consistent with the predictions of the Standard Model and supersede the previous results on these gauge coupling parameters published by Delphi.
  European Physical Journal C 04/2012; 66(1):35-56. · 3.63 Impact Factor
• Article: Correlations between polarisation states of W particles in the reaction e−e+→W−W+ at LEP2 energies 189–209 GeV

  The DELPHI Collaboration, J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, [......], M. Winter, M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan
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  ABSTRACT: In a study of the reaction e − e +→W − W + with the DELPHI detector, the probabilities of the two W particles occurring in the joint polarisation states transverse–transverse (TT), longitudinal–transverse plus transverse–longitudinal (LT) and longitudinal–longitudinal (LL) have been determined using the final states WW®lnq[`(q)]WW{\rightarrow}l\nu q\bar{q} (l=e,μ). The two-particle joint polarisation probabilities, i.e. the spin density matrix elements ρ TT , ρ LT , ρ LL , are measured as functions of the W − production angle, qW-\theta _{W^{-}}, at an average reaction energy of 198.2GeV. Averaged over all cosqW-\cos\theta_{W^{-}}, the following joint probabilities are obtained: [`(r)]TT=(67±8)%,\bar{\rho}_{TT}=(67\pm8)\%, [`(r)]LT=(30±8)%,\bar{\rho}_{LT}=(30\pm8)\%, [`(r)]LL=(3±7)%.\bar{\rho}_{LL}=(3\pm7)\%. These results are in agreement with the Standard Model predictions of 63.0%, 28.9% and 8.1%, respectively. The related polarisation cross-sections σ TT , σ LT and σ LL are also presented.
  European Physical Journal C 04/2012; 63(4):611-623. · 3.63 Impact Factor
• Article: Investigation of Colour Reconnection in WW events with the DELPHI detector at LEP-2

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: In the reaction e+e-→WW→(q1q̄2)(q3q̄4) the usual hadronization models treat the colour singlets q1q̄2 and q3q̄4 coming from two W bosons independently. However, since the final state partons may coexist in space and time, cross-talk between the two evolving hadronic systems may be possible during fragmentation through soft gluon exchange. This effect is known as colour reconnection. In this article the results of the investigation of colour reconnection effects in fully hadronic decays of W pairs in DELPHI at LEP are presented. Two complementary analyses were performed, studying the particle flow between jets and W mass estimators, with negligible correlation between them, and the results were combined and compared to models. In the framework of the SK-I model, the value for its κ parameter most compatible with the data was found to be: κSK-I=2.2+2.5 -1.3 corresponding to the probability of reconnection P\textreco\mathcal{P}_{\text{reco}} to be in the range 0.31 < P\textreco < 0.680.31
  European Physical Journal C 04/2012; 51(2):249-269. · 3.63 Impact Factor
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  Available from: Jiri Masik

  Article: Study of the dependence of direct soft photon production on the jet characteristics in hadronic Z0 decays

  The DELPHI Collaboration, J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, [......], M. Winter, M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan
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  ABSTRACT: An analysis of the direct soft photon production rate as a function of the parent jet characteristics is presented, based on hadronic events collected by the DELPHI experiment at LEP1. The dependences of the photon rates on the jet kinematic characteristics (momentum, mass, etc.) and on the jet charged, neutral and total hadron multiplicities are reported. Up to a scale factor of about four, which characterizes the overall value of the soft photon excess, a similarity of the observed soft photon behavior to that of the inner hadronic bremsstrahlung predictions is found for the momentum, mass, and jet charged multiplicity dependences. However for the dependence of the soft photon rate on the jet neutral and total hadron multiplicities a prominent difference is found for the observed soft photon signal as compared to the expected bremsstrahlung from final state hadrons. The observed linear increase of the soft photon production rate with the jet total hadron multiplicity and its strong dependence on the jet neutral multiplicity suggest that the rate is proportional to the number of quark pairs produced in the fragmentation process, with the neutral pairs being more effectively radiating than the charged ones.
  European Physical Journal C 04/2012; 67(3):343-366. · 3.63 Impact Factor
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  Available from: Jiri Masik

  Article: Measurement of the mass and width of the W boson in e+e- collisions at = 161–209 GeV

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: A measurement of the W boson mass and width has been performed by the DELPHI collaboration using the data collected during the full LEP2 programme (1996–2000). The data sample has an integrated luminosity of 660pb-1 and was collected over a range of centre-of-mass energies from 161 to 209GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the W+W-→ℓν̄ℓqq̄’ and W+W-→qq̄’q̄q’ channels. The W mass result for the combined data set is MW = 80.336 ±0.055 (\textStat.) ±0.028 (\textSyst.) ±0.025 (\textFSI) ±0.009 (\textLEP) \textGeV/c2, M_W = 80.336 \pm0.055 ({\text{Stat.}}) \pm0.028 ({\text{Syst.}}) \pm0.025 ({\text{FSI}}) \pm0.009 ({\text{LEP}}) \text{GeV}/c^2, where FSI represents the uncertainty due to final state interaction effects in the qq̄’q̄q’ channel, and LEP represents that arising from the knowledge of the collision energy of the accelerator. The combined value for the W width is GW = 2.404 ±0.140 (\textStat.) ±0.077 (\textSyst.) ±0.065 (\textFSI) \textGeV/c2. {\Gamma_{W}} = 2.404 \pm0.140 ({\text{Stat.}}) \pm0.077 ({\text{Syst.}}) \pm0.065 ({\text{FSI}}) \text{GeV}/c^2. These results supersede all values previously published by the DELPHI collaboration.
  European Physical Journal C 04/2012; 55(1):1-38. · 3.63 Impact Factor
• Article: TERA high gradient test program of RF cavities for medical linear accelerators

  A. Degiovanni, U. Amaldi, R. Bonomi, M. Garlasché, A. Garonna, S. Verdú-Andrés, R. Wegner
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  ABSTRACT: The scientific community and the medical industries are putting a considerable effort into the design of compact, reliable and cheap accelerators for hadrontherapy. Up to now only circular accelerators are used to deliver beams with energies suitable for the treatment of deep seated tumors. The TERA Foundation has proposed and designed a hadrontherapy facility based on the cyclinac concept: a high gradient linear accelerator placed downstream of a cyclotron used as an injector. The overall length of the linac, and therefore its final cost, is almost inversely proportional to the average accelerating gradient achieved in the linac.TERA, in collaboration with the CLIC RF group, has started a high gradient test program. The main goal is to study the high gradient behavior of prototype cavities and to determine the appropriate linac operating frequency considering important issues such as machine reliability and availability of distributed power sources. A preliminary test of a 3 GHz cavity has been carried out at the beginning of 2010, giving encouraging results. Further investigations are planned before the end of 2011. A set of 5.7 GHz cavities is under production and will be tested in a near future. The construction and test of a multi-cell structure is also foreseen.
  Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 10/2011; 657:55-58. · 1.21 Impact Factor
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  Available from: arxiv.org

  Article: Cyclinac Medical Accelerators Using Pulsed C6+/H2+ Ion Sources

  A. Garonna, U. Amaldi, R. Bonomi, D. Campo, A. Degiovanni, M. Garlasché, I. Mondino, V. Rizzoglio, S. Verdú Andrés
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  ABSTRACT: Charged particle therapy, or so-called hadrontherapy, is developing very rapidly. There is large pressure on the scientific community to deliver dedicated accelerators, providing the best possible treatment modalities at the lowest cost. In this context, the Italian research Foundation TERA is developing fast-cycling accelerators, dubbed 'cyclinacs'. These are a combination of a cyclotron (accelerating ions to a fixed initial energy) followed by a high gradient linac boosting the ions energy up to the maximum needed for medical therapy. The linac is powered by many independently controlled klystrons to vary the beam energy from one pulse to the next. This accelerator is best suited to treat moving organs with a 4D multi-painting spot scanning technique. A dual proton/carbon ion cyclinac is here presented. It consists of an Electron Beam Ion Source, a superconducting isochronous cyclotron and a high-gradient linac. All these machines are pulsed at high repetition rate (100-400 Hz). The source should deliver both C6+ and H2+ ions in short pulses (1.5 {\mu}s flat-top) and with sufficient intensity (at least 108 fully stripped carbon ions at 300 Hz). The cyclotron accelerates the ions to 120 MeV/u. It features a compact design (with superconducting coils) and a low power consumption. The linac has a novel C-band high gradient structure and accelerates the ions to variable energies up to 400 MeV/u. High RF frequencies lead to power consumptions which are much lower than the ones of synchrotrons for the same ion extraction energy. This work is part of a collaboration with the CLIC group, which is working at CERN on high-gradient electron-positron colliders. Comment: Submitted to Journal of Instrumentation, as proceedings of EBIST2010 (25 June 2010) 13 pages, 8 figures Revised version submitted on 11 August 2010, 18 pages, 9 figures
  07/2010;
• Article: Di-jet production in γ γ collisions at LEP2

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan, DELPHI Collaboration
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  ABSTRACT: The production of two high-p T jets in the interactions of quasi-real photons in e + e − collisions at Ö{see}\sqrt{s_{ee}} from 189GeV to 209GeV is studied with data corresponding to an integrated e + e − luminosity of 550pb−1. The jets reconstructed by the k ⊥ -cluster algorithm are defined within the pseudo-rapidity range −1<η<1 and with jet transverse momentum, p T , above 3GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum [`(pT)]\overline{p_{T}} of the jets and is compared to perturbative QCD calculations.
  European Physical Journal C 11/2008; 58(4):531-541. · 3.63 Impact Factor
• Article: Observation of the muon inner bremsstrahlung at LEP1

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P. P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N. I. Zimin, A. Zintchenko, M. Zupan, DELPHI Collaboration
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  ABSTRACT: Muon bremsstrahlung photons converted in front of the DELPHI main tracker (TPC) in dimuon events at LEP1 were studied in two photon kinematic ranges: 0.2<E γ ≤1GeV and transverse momentum with respect to the parent muon p T <40MeV/c, and 1<E γ ≤10GeV and p T <80MeV/c. A good agreement of the observed photon rate with predictions from QED for the muon inner bremsstrahlung was found, contrary to the anomalous soft photon excess that has been observed recently in hadronic Z 0 decays. The obtained ratios of the observed signal to the predicted level of the muon bremsstrahlung are 1.06±0.12±0.07 in the photon energy range 0.2<E γ ≤1GeV and 1.04±0.09±0.12 in the photon energy range 1<E γ ≤10GeV. The bremsstrahlung dead cone is observed for the first time in the direct photon production at LEP.
  European Physical Journal C 09/2008; 57(3):499-514. · 3.63 Impact Factor
• Article: Study of W-boson polarisations and triple gauge boson couplings in the reaction e+e-→W+W- at LEP 2

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: A determination of the single W spin density matrix (SDM) elements in the reaction e+e-→W+W-→lνqq̄(l=e/μ) is reported at centre-of-mass energies between 189 and 209 GeV. The data sample used corresponds to an integrated luminosity of 520 pb-1 taken by DELPHI between 1998 and 2000. The single W SDM elements, ρττ’ W± (τ,τ’=± 1 or 0), are determined as a function of the W- production angle with respect to the e- beam direction and are obtained from measurements of the W decay products by the application of suitable projection operators, Λττ’, which assume the V-A coupling of the W-boson to fermions. The measured SDM elements are used to obtain the fraction of longitudinally polarised Ws, with the result: \fracs\textLs\texttot = 24.9 ±4.5(\textstat) ±2.2(\textsyst)%\frac{\sigma_{\text{L}}}{\sigma_{{\text{tot}}}} = 24.9 \pm4.5({\text{stat}}) \pm2.2({\text{syst}})\% at a mean energy of 198 GeV. The SDM elements are also used to determine the triple gauge couplings Δg1 Z,Δκγ,λγ and g4 Z, [(k)\tilde]Z\tilde{\kappa}_{Z} and [(l)\tilde]Z\tilde{\lambda}_{Z}. For the CP-violating couplings the results of single parameter fits are: g4Z = -0.39+0.19-0.20g_4^{{Z}} = -0.39^{+0.19}_{-0.20} [(k)\tilde]Z = -0.09+0.08-0.05\tilde{\kappa}_{{Z}} = -0.09^{+0.08}_{-0.05} [(l)\tilde]Z = -0.08±0.07 .\tilde{\lambda}_{{Z}} = -0.08\pm0.07 . The errors are a combination of statistical and systematic errors. All results are consistent with the Standard Model.
  European Physical Journal C 03/2008; 54(3):345-364. · 3.63 Impact Factor
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  Available from: Francisco Matorras

  Article: Study of b-quark mass effects in multijet topologies with the DELPHI detector at LEP

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: The effect of the heavy b-quark mass on the two, three and four-jet rates is studied using LEP data collected by the DELPHI experiment at the Z peak in 1994 and 1995. The rates of b-quark jets and light quark jets (ℓ=uds) in events with n=2, 3, and 4 jets, together with the ratio of two and four-jet rates of b-quarks with respect to light-quarks, Rn bℓ, have been measured with a double-tag technique using the CAMBRIDGE jet-clustering algorithm. A comparison between experimental results and theory (matrix element or Monte Carlo event generators such as PYTHIA, HERWIG and ARIADNE) is done after the hadronisation phase. Using the four-jet observable R4 bℓ, a measurement of the b-quark mass using massive leading-order calculations gives: mb(MZ) = 3.76 ±0.32 (\textstat) ±0.17 (\textsyst) ±0.22 (\texthad) ±0.90 (\texttheo)\textGeV/c2.m_b(M_Z) = 3.76 \pm0.32 ({\text{stat}}) \pm0.17 ({\text{syst}}) \pm0.22 ({\text{had}}) \pm0.90 ({\text{theo}})\,\text{GeV}/c^2\,. This result is compatible with previous three-jet determinations at the MZ energy scale and with low energy mass measurements evolved to the MZ scale using QCD renormalisation group equations.
  European Physical Journal C 01/2008; 55(4):525-538. · 3.63 Impact Factor
• Article: Study of triple-gauge-boson couplings ZZZ, ZZγ and Zγγ at LEP

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: Neutral triple-gauge-boson couplings ZZZ, ZZγ and Zγγ have been studied with the DELPHI detector using data at energies between 183 and 208GeV. Limits are derived on these couplings from an analysis of the reactions e+e-→Zγ, using data from the final states γff̄, with f=q or ν, from e+e-→ZZ, using data from the four-fermion final states qq̄qq̄, qq̄μ+μ-, qq̄e+e-, qq̄νν̄, μ+μ-νν̄ and e+e-νν̄, and from e+e-→Zγ*, in which the final state γ is off mass-shell, using data from the four-fermion final states qq̄e+e- and qq̄μ+μ-. No evidence for the presence of such couplings is observed, in agreement with the predictions of the Standard Model.
  European Physical Journal C 07/2007; 51(3):525-542. · 3.63 Impact Factor
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  Available from: Jiri Masik

  Article: Zγ* production in e+e- interactions at

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: Measurements of Zγ* production are presented using data collected by the DELPHI detector at centre-of-mass energies ranging from 183 to 209GeV, corresponding to an integrated luminosity of about 667pb-1. The measurements cover a wide range of the possible final state four-fermion configurations: hadronic and leptonic (e+e-qq̄, μ+μ-qq̄, qq̄νν̄), fully leptonic (l+l-l’+l’-) and fully hadronic final states (qq̄qq̄, with a low mass qq̄ pair). Measurements of the Zγ* cross-section for the various final states have been compared with the Standard Model expectations and found to be consistent within the errors. In addition, a total cross-section measurement of the l+l-l’+l’- cross-section is reported, and found to be in agreement with the prediction of the Standard Model.
  European Physical Journal C 07/2007; 51(3):503-523. · 3.63 Impact Factor
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  Available from: Jiri Masik

  Article: Search for a fourth generation b’-quark at LEP-II at 196–209 GeV

  J. Abdallah, P. Abreu, W. Adam, P. Adzic, T. Albrecht, R. Alemany-Fernandez, T. Allmendinger, P.P. Allport, U. Amaldi, N. Amapane, [......], M. Witek, O. Yushchenko, A. Zalewska, P. Zalewski, D. Zavrtanik, V. Zhuravlov, N.I. Zimin, A. Zintchenko, M. Zupan, The DELPHI Collaboration
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  ABSTRACT: A search for the pair production of fourth generation b’-quarks was performed using data taken by the DELPHI detector at LEP-II. The analysed data were collected at centre-of-mass energies ranging from 196 to 209GeV, corresponding to an integrated luminosity of 420pb-1. No evidence for a signal was found. Upper limits on BR(b’→bZ) and BR(b’→cW) were obtained for b’ masses ranging from 96 to 103GeV/c 2. These limits, together with the theoretical branching ratios predicted by a sequential four generations model, were used to constrain the value of R\textCKM=|\fracVcb¢V\texttb¢Vtb|R_{\text{CKM}}=|\frac{V_{cb\prime}}{V_{\text{tb}\prime}V_{tb}}|, where Vcb′, Vtb′ and Vtb are elements of the extended CKM matrix.
  European Physical Journal C 03/2007; 50(3):507-518. · 3.63 Impact Factor