2,191 research outputs found

    Early Standard Model Physics and Early Discovery Strategy in CMS

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    Although hadron colliders like the LHC are constructed for exploring new physics at higher energies, data-sets will be largely dominated by Standard Model processes. Especially in the early stage of running, it will be important to understand this overwhelming Standard Model continuum prior to any dedicated search for new physics. This paper covers CMS perspectives for early Standard Model physics and early discovery of new processes. It is shown how key Standard Model processes can be measured at low integrated luminosity. Plans for early discovery of physics beyond the Standard Model with 1 fb-1 or less are then discussed

    Search for anomalously coupling and fermiophobic Higgs Bosons

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    Searches for fermiophobic Higgs boson decaying into photon or weak boson pairs have been performed at LEP with the data collected at center of mass energies up to 209 GeV. A summary of several analyses allowing to cover some hundred different final state topologies is presented. No statistically significant evidence of fermiophobic Higgs boson has been found. A lower limit on the Higgs boson mass is presented. More generally, anomalous couplings of the Higgs boson are searched for through the processes e +e − → H 0 γ, e +e − → e +e −H 0 and e +e − → H 0Z by the L3 collaboration. The Higgs decay channels H 0 → ff, H 0 → γγ, H 0 → Zγ and H 0 → WW(∗) are considered and no evidence is found for anomalous Higgs production or decay and limits are put

    Study of associated WH production with H -> WW* in the 3 leptons final state

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    In order to evaluate the physics potential of the CMS detector, the WH associated production of a Higgs boson decaying into a W pair is studied. Performance of the data acquisition and the sophisticated trigger system, particle identification and event reconstruction are investigated by performing a detailed analysis on simulated data. Three-lepton final states are shown to provide interesting possibilities. For an integrated luminosity of 100fb^-1, a potential signal significance of more than 5 sigma is obtained in the mass interval between 155 and 178 GeV/c^2. The corresponding precision on the Higgs boson mass and partial decay width into W pairs are evaluated. This channel also provides one of the very few possible avenues towards the discovery of a fermiophobic Higgs boson below 180 GeV/c^2

    A tool-supported approach to inter-tabular verification.

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    The use of decision tables to verify KBS has been advocated several times in the V&V literature. However, one of the main drawbacks of those system is that they fail to detect anomalies which occur over rule chains. In a decision table based context this means that anomalies which occur due to interactions between tables are neglected. These anomalies are called inter-tabular anomalies. In this paper we investigate an approach that deals with inter-tabular anomalies. One of the prerequisites for the approach was that it could be used by the knowledge engineer during the development of the KBS. This requires that the anomaly check can be performed on-line. As a result, the approach partly uses heuristics where exhaustive checks would be too inefficient. All detection facilities that will be described, have been implemented in a table-based development tool called PROLOGA. The use of this tool will be briefly illustrated. In addition, some experiences in verifying large knowledge bases are discussed.

    Timing of the CMS tracker: Study of module properties

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    One of the crucial aspects of the commissioning of the CMS silicon tracker will be the absolute timing of each module, to accommodate both delays introduced by the hardware configuration and effects due to the time-of-flight of particles. The objective is to be optimally synchronized with the bunch-crossing to maximize the efficiency while minimizing the number of remnant hits from the adjacent bunch-crossings. In the present note, a procedure to reach that goal is deduced from the analysis of results obtained on a simple test setup. Emphasis is put on the parametrization of the pulse shape and on the effect of capacitive coupling between adjacent strips.It is shown that the pulse from the leading strip must be used as a reference during the timing procedure, in order to have asymmetric efficiency over consecutive bunch crossings and to avoid fake clusters

    MoMEMta, a modular toolkit for the Matrix Element Method at the LHC

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    The Matrix Element Method has proven to be a powerful method to optimally exploit the information available in detector data. Its widespread use is nevertheless impeded by its complexity and the associated computing time. MoMEMta, a C++ software package to compute the integrals at the core of the method, provides a versatile implementation of the Matrix Element Method to both the theory and experiment communities. Its modular structure covers the needs of experimental analysis workflows at the LHC without compromising ease of use on simpler and smaller simulated samples used for phenomenological studies. With respect to existing tools, MoMEMta improves on usability and flexibility. In this paper, we present version 1.0 of MoMEMta, together with examples illustrating the wide range of applications at the LHC accessible for the first time with a single tool.Comment: 18 pages, 3 figures; post peer revie

    Holocene variations in Lake Titicaca water level and their implications for sociopolitical developments in the central Andes

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    Holocene climate in the high tropical Andes was characterized by both gradual and abrupt changes, which disrupted the hydrological cycle and impacted landscapes and societies. High-resolution paleoenvironmental records are essential to contextualize archaeological data and to evaluate the sociopolitical response of ancient societies to environmental variability. Middle-to-Late Holocene water levels in Lake Titicaca were reevaluated through a transfer function model based on measurements of organic carbon stable isotopes, combined with high-resolution profiles of other geochemical variables and paleoshoreline indicators. Our reconstruction indicates that following a prolonged low stand during the Middle Holocene (4000 to 2400 BCE), lake level rose rapidly ~15 m by 1800 BCE, and then increased another 3 to 6 m in a series of steps, attaining the highest values after ~1600 CE. The largest lake-level increases coincided with major sociopolitical changes reported by archaeologists. In particular, at the end of the Formative Period (500 CE), a major lake-level rise inundated large shoreline areas and forced populations to migrate to higher elevation, likely contributing to the emergence of the Tiwanaku culture

    Functional outcomes and complications after salvage total laryngectomy for residual, recurrent, and second primary squamous cell carcinoma of the larynx and hypopharynx : a multicenter retrospective cohort study

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    Background/Purpose: We analyzed complications and functional outcomes and aimed at identifying prognostic factors for functional outcomes and complications in patients who underwent salvage total laryngectomy (STL) for residual, recurrent, and second primary squamous cell carcinoma (SCC) of the larynx and hypopharynx after initial (chemo)radiation. Methods: Retrospective cohort study of patients who underwent STL in four major Belgian reference hospitals between 2002 and 2018. Prognostic factors for functional outcomes and complications were identified with uni- and multivariable analysis. Results: A total of 405 patients were included in the final analysis. STL was performed for residual tumor (40.2%), local recurrence (40.5%), or second primary laryngeal or hypopharyngeal SCC (19.4%). Early postoperative complications were experienced by 34.2% of patients: postoperative hemorrhage occurred in 5.4%, wound infection in 16.2%, and clinical pharyngocutaneous fistula (PCF) in 25.5% of patients. Early readmission proved necessary in 15.1% of cases, most often due to late PCF development (72.2%). Patients achieved total peroral intake in 94.2% of cases. However, subjective dysphagia was reported by 31.3% of patients during follow-up. Functional speech, defined as functional communication by speech without additional aids, was reported in 86.7% of cases and was most often achieved by tracheo-esophageal puncture (TEP) (94.1%). In a multivariable model, lower preoperative hemoglobin (<12.5 g/dl) was identified as an independent prognostic factor for higher overall complication rate. No risk factors were found significant for clinical fistula formation. Vascularized tissue augmentation did not significantly prevent clinical PCF. Patients with positive section margins, patients initially treated with surgery combined with adjuvant RT (vs. radiotherapy alone), and those developing PCF after STL were less likely to achieve total peroral intake. Postoperative dysphagia proved more likely in patients who developed a PCF postoperatively, and less likely in patients who underwent STL without partial pharyngectomy and in patients with myocutaneous pectoralis major (PM) flap reconstruction, compared to muscle onlay PM flap. Achieving postoperative functional speech proved most likely in patients with smaller tumors (lower pT classification) and free section margins. Conclusion: Substantial complication rates and favorable functional outcomes are reported after STL

    Procedure for the fine delay adjustment of the CMS tracker

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    One of the crucial aspects of the commissioning of the CMS silicon tracker will be the absolute timing adjustment of each module, to accommodate both delays introduced by the hardware configuration and effects due to the time of flight of particles. The objective is to be optimally synchronized with the bunch-crossing to maximize the efficiency while minimizing the number of remnant hits from the adjacent bunch-crossings. In the present note, a procedure to reach that goal is studied. Monte Carlo studies as well as the analysis of data from the commissioning of the detector are used to assess the time needed and the resolution that can be achieved. Critical aspects are discussed, and results from the first implementation are presented
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