6,265 research outputs found

    Higgs Searches at LEP and at the Tevatron

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    After years of efforts to push the LEP performance to, and indeed beyond, the limits of what had been believed possible, hints of signal of a Higgs boson at 115GeV/c2 appeared in June 2000, were confirmed in September, and confirmed again in November. Spending an additional six-month period with LEP would have given the unambiguous opportunity of a fundamental discovery. Instead, this possibilty was handed over to the Tevatron, for which at least si more years will be needed to confirm the existence of a Higgs boson around 115GeV/c2. The upgrades performed at LEP and needed at the Tevatron, together with the physics outcomes, are briefly mentioned in turn.Comment: 20 pages, 9 figures, Physics in Collisions, June 2001, Seou

    SUSY Decays of Higgs Particles

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    Among the possible decay modes of Higgs particles into supersymmetric states, neutralino and chargino decays play a prominent r\^ole. The experimental opportunities of observing such decay modes at LEP2 and at future e+e- linear colliders are analyzed within the frame of the Minimal Supersymmetric extension of the Standard Model. For heavy Higgs particles, the chargino/neutralino decay modes can be very important, while only a small window is open for the lightest CP-even Higgs particle. If charginos/neutralinos are found at LEP2, such decay modes can be searched for in a small area of the parameter space, and invisible decays may reduce the exclusion limits of the lightest CP-even Higgs particle slightly; if charginos/neutralinos are not found at LEP2 in direct searches, the Higgs search will not be affected by the SUSY particle sector.Comment: 13 pages including 4 figures, uses latex and (e)psfig.st

    How Should We Organize the Higgs Safari?

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    Searches for new particles at LEP

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    The most recent developments in the domain of new particle searches at LEP are reviewed. In particular, the updates of the searches for the standard model Higgs boson and for the Higgs bosons of the MSSM are summarized. A new method is proposed to derive a 95% C.L. limit on the standard model Higgs boson mass from the combinations of the analyses of the four LEP experiments. Finally, two monojet events from ALEPH with unexpectedly large transverse momenta and invariant masses are presented

    Balance Sheet Effects in Currency Crises: Evidence from Brazil

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    "Third-generation currency crises models" argue that capital losses from exchange-rate depreciation propagate the crises to the productive sector. To test these models, we use a firm-level dataset that allows us to measure currency mismatches around the 2002 Brazilian currency crisis. We find that, between 2001 and 2003, firms that shortly before the crisis had large currency mismatches decreased their investment rates by 8.1 percentual points, relatively to other public firms. Moreover, we show that the currency depreciation implied large competitive gains for the exporters, and yet the investment of exporters with large currency mismatches fell by 12.5 percentual points, relatively to other exporters. The estimated falls in investment are economically very relevant, thereby corroborating the relevance of third generation models negative balance sheet effects.

    Balance Sheet Effects in Currency Crises: Evidence from Brazil

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    In third generation currency crises models, balance sheet losses from currency depreciations propagate the crises into the real sector of the economy. To test these models, we built a firmlevel database that allowed us to measure currency mismatches around the 2002 Brazilian currency crisis. We found that between 2001 and 2003, firms with large currency mismatches just before the crisis reduced their investment rates 8.1 percentage points more than other publicly held firms. We also showed that the currency depreciation increased exporters revenue, but those with currency mismatches reduced investments 12.5 percentage points more than other exporters. These estimated reductions in investment are economically very significant, underscoring the importance of negative balance sheet effects in currency crises. Jel Codes:F32; F34; G31; G32Investment; Balance sheets; Currency crises; Hedge; Financial constraints.

    TLEP, first step in a long-term vision for HEP

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    The discovery of H(126) has renewed interest in circular e+e- colliders that can operate as Higgs factories, which benefit from three unique characteristics: i) high luminosity and reliability, ii) the availability of several interaction points, iii) superior beam energy accuracy. TLEP is an e+e- storage ring of 80-km circumference that can operate with very high luminosity from the Z peak (90 GeV) to the top quark pair threshold (350 GeV). It can achieve transverse beam polarization at the Z peak and WW threshold, giving it unparalleled accuracy on the beam energy. A preliminary study indicates that an 80 km tunnel could be constructed around CERN. Such a tunnel would allow a 100 TeV proton-proton collider to be established in the same ring (VHE-LHC), offering a long term vision.Comment: This is a contribution to the the Snowmass process 2013: Frontier Capabilitie

    Combining limits

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    L'héritage des collisionneurs LEP et TeVatron

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    Les quinze derni√®res ann√©es du pr√©c√©dent mill√©naire ont donn√© lieu, gr√Ęce √† l'av√®nement de trois projets majeurs en Physique des Hautes √©nergies, √† une moisson de r√©sultats permettant une meilleure compr√©hension des m√©canismes r√©gissant l'√©volution de l'Univers. Le LEP et le SLC, d'une part, et le TeVatron, d'autre part, ont recueilli pendant plus d'une d√©cennie les fruits des collisions √©lectron-positon et proton-antiproton avec une √©nergie et une pr√©cision jamais atteintes auparavant. Nous nous concentrerons ici sur la finesse et la port√©e fondamentale de ces mesures de pr√©cision, et nous concluerons par les signes avant-coureurs de probables futures d√©couvertes

    Comments on "Wall-plug (AC) power consumption of a very high energy e+/e- storage ring collider" by Marc Ross

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    The paper arXiv:1308.0735 questions some of the technical assumptions made by the TLEP Steering Group when estimating in arXiv:1305.6498 the power requirement for the very high energy e+e- storage ring collider TLEP. We show that our assumptions are based solidly on CERN experience with LEP and the LHC, as well accelerators elsewhere, and confirm our earlier baseline estimate of the TLEP power consumption.Comment: 6 page
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