Eduardo Nebot del Busto

Bubble Technology Industries · Research and Development

A distributed beam loss monitoring system, named the optical fibre Beam Loss Monitor, has been installed at the Australian Synchrotron. Relativistic charged particles produced in beam loss events generate photons via the Cherenkov mechanism in four silica fibres that run parallel to the beam pipe and cover the majority of the accelerator's length....

The main detector type for beam loss monitoring of the LHC is a parallel plate Ionization Chamber (IC). In the locations where the beam losses could saturate the read-out electronics of the ICs, two other monitor types, Little Ionization Chambers (LIC) and Secondary Emission Monitors, have been installed to extend the dynamic range of the ICs. The...

The Compact Linear Collider (CLIC) is a multi-TeV high-luminosity linear e+e− collider under development. For an optimal exploitation of its physics potential, CLIC is foreseen to be built and operated in a staged approach with three centre-of-mass energy stages ranging from a few hundred GeV up to 3 TeV. The first stage will focus on precision Sta...

A measurement of the cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a centre-of-mass energy of \( \sqrt{s}=8 \) TeV is presented. The measurement covers the pseudorapidity ranges |η γ | < 1.37 and 1.56 ≤ |η γ | < 2.37 in the transverse energy range 25 < E T γ < 1500 GeV. The results are based on...

Due to the secondary showers generated when a particle hits the vacuum chamber, beam losses at an accelerator may be detected via radiation detectors located near the beam line. Several sources of background can limit the sensitivity and reduce the dynamic range of a Beam Loss Monitor (BLM). This document concentrates on potential sources of backgr...

In total, over 5700 changes to the BLM thresholds were made during 2015. The new thresholds are based on the operational experience from Run 1, on new simulation models and on results from quench tests performed so far. Following the first experiences with operation at 6.5 TeV, a series of adjustments were made throughout the first operational year...

Beam loss mon­i­tor­ing sys­tems based on op­ti­cal fi­bres (oBLM), have been under con­sid­er­a­tion for fu­ture col­lid­ers for sev­eral years. To dis­tin­guish losses be­tween con­sec­u­tive quadrupoles, a po­si­tion res­o­lu­tion of less than 1 m is re­quired. A res­o­lu­tion of bet­ter than 0.5 m has been achieved in ma­chines with sin­gle, na...

The Com­pact Lin­ear Col­lider (CLIC) is a pro­posal for a fu­ture lin­ear e+-e− ac­cel­er­a­tor that can reach 3 TeV cen­tre of mass en­ergy. It is based on a two-beam ac­cel­er­a­tion scheme, with two ac­cel­er­a­tors op­er­at­ing in par­al­lel. One of the main CLIC el­e­ments is a 2 m long two-beam mod­ule where power from a high in­ten­sity, lo...

The Beam Loss Monitoring (BLM) system of the LHC consists of over 3600 ionization chambers. The main task of the system is to prevent the superconducting magnets from quenching and protect the machine components from damage, as a result of critical beam losses. The BLM system therefore requests a beam abort when the measured dose in the chambers ex...

In the years 2009-2013 the Large Hadron Collider (LHC) has been operated with the top beam energies of 3.5 TeV and 4 TeV per proton (from 2012) instead of the nominal 7 TeV. The currents in the superconducting magnets were reduced accordingly. To date only seventeen beam-induced quenches have occurred; eight of them during specially designed quench...

Silicon Photomultipliers (SiPMs) are well recognised as very competitive photodetectors due to their exceptional photon number and time resolution, room-temperature low-voltage operation, insensitivity to magnetic fields, compactness, and robustness. Detection of weak light pulses of nanosecond time scale appears to be the best area for SiPM applic...

The unprecedented requirements that new machines are setting on their diagnostic systems is leading to the devel-opment of new generation of devices with large dynamic range, sensitivity and time resolution. Beam loss detec-tion is particularly challenging due to the large extension of new facilities that need to be covered with localized detector....

The Compact Linear Collider (CLIC) is an e+/e- collider based on the two-beam acceleration principle, proposed to support precision high-energy physics experiments in the energy range 0.5-3 TeV [1]. To achieve a high luminosity of up to 6×1034cm-2s-1, the transport and preservation of a low emittance beam is mandatory. A large number and great vari...

The unprecedented requirements that new machines are setting on their diagnostic systems is leading to the development of new generation of devices with large dynamic range, sensitivity and time resolution. Beam loss detection is particularly challenging due to the large extension of new facilities that need to be covered with localized detector. C...

The primary role of the beam loss monitoring (BLM) system for the compact linear collider (CLIC) study is to work within the machine protection system. Due to the size of the CLIC facility, a BLM that covers large distances along the beam line is highly desirable, in particular for the CLIC drive beam decelerators, which would alternatively require...

A search is made for massive long-lived highly ionising particles with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at sqrt(s)=7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section...

Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having different acceptances, systematic uncertainties and sensitivity to background. The ratios of th...

The energy stored in the nominal LHC beams is two times 362 MJ, 100 times the energy of the Tevatron. As little as 1mJ/cm(3) deposited energy quenches a magnet at 7 TeV and 1 J/cm(3) causes magnet damage. The beam dumps are the only places to safely dispose of this beam. One of the key systems for machine protection is the beam loss monitoring (BLM...

The local hadronic calibration scheme developed for the reconstruction and calibration of jets and missing transverse energy in ATLAS has been evaluated using data obtained during combined beam tests of modules of the ATLAS liquid argon endcap and forward calorimeters. These tests covered the pseudorapidity range of 2.5 < vertical bar eta vertical...

A search is reported for the pair production of a new quark b' with at least one b' decaying to a Z boson and a bottom quark. The data, corresponding to 2.0 fb(-1) of integrated luminosity, were collected from pp collisions at √s = 7 TeV with the ATLAS detector at the CERN Large Hadron Collider. Using events with a b-tagged jet and a Z boson recons...

A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming subsequent decay to a W boson and a b quark, t't[over ¯]'→W(+)bW(-)b[over ¯]. The search is based on 1.04 fb(-1) of proton-proton collisions at √[s]=7 TeV collected by the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in...

This Letter describes a model-independent search for the production of new resonant states in photon+jet events in 2.11 fb(-1) of proton-proton collisions at √s=7 TeV. We compare the photon+jet mass distribution to a background model derived from data and find consistency with the background-only hypothesis. Given the lack of evidence for a signal,...

A search is presented for gluinos decaying via the supersymmetric partner of the top quark using events with two same-sign leptons, jets, and missing transverse momentum. The analysis is performed with 2.05 fb(-1) of integrated luminosity from pp collisions at sqrt[s]=7 TeV collected by the ATLAS detector at the LHC. No excess beyond the standard m...

A search for the decay of a light Higgs boson (120-140 GeV) to a pair of weakly interacting, long-lived particles in 1.94 fb(-1) of proton-proton collisions at sqrt[s] = 7 TeV recorded in 2011 by the ATLAS detector is presented. The search strategy requires that both long-lived particles decay inside the muon spectrometer. No excess of events is ob...

A measurement of spin correlation in tt[over ¯] production is reported using data collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 2.1 fb(-1). Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. The difference in azimuthal angle between the two...

This Letter presents a search for tb resonances in 1.04 fb(-1) of LHC proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 7 TeV. Events with a lepton, missing transverse momentum, and two jets are selected and the invariant mass of the corresponding final state is reconstructed. The search exploits the shape o...

This Letter presents a search for pair production of heavy down-type quarks decaying via b' → Wt in the lepton + jets channel, as b'b' → W- tW+ t → bbW+ W- W+ W- → l± νbbqqqqqq. In addition to requiring exactly one lepton, large missing transverse momentum, and at least six jets, the invariant mass of nearby jet pairs is used to identify high trans...

A QCD analysis is reported of ATLAS data on inclusive W^{±} and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x∼0.01. Specifically, the data support the hypothesis of a symmetric composition of t...

This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark (t~) in the e ± μ ∓ continuum using 2.1 fb−1 of data collected by the ATLAS detector in s√=7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-vi...

Unidentified falling objects (UFOs) are potentially a major luminosity limitation for nominal LHC operation. They are presumably micrometer sized dust particles which lead to fast beam losses when they interact with the beam. With large-scale increases and optimizations of the beam loss monitor (BLM) thresholds, their impact on LHC availability was...

The results of a search for pair production of the scalar partners of bottom quarks in 2.05  fb(-1) of pp collisions at sqrt[s]=7  TeV using the ATLAS experiment are reported. Scalar bottom quarks are searched for in events with large missing transverse momentum and two jets in the final state, where both jets are identified as originating from a b...

A measurement of the production cross-section for top quark pairs (tt¯) in pp collisions at s=7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in the single lepton topology by requiring an electron or muon, large missing transverse momentum and at least three jets. With a data sample o...

The χ(b)(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider at sqrt[s] = 7  TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4  fb(-1), these states are reconstructed through their radiative decays to Υ(1S,2S) with Υ → μ+ μ-. In addition to the mass p...

This Letter presents a search for the Standard Model Higgs boson in the decay channel H→ZZ→ℓ+ℓ-ℓℓ, where ℓ,ℓ′=e or μ, using proton-proton collisions at s=7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb-1. The four-lepton invariant mass distribution is compared with Standard Model background expectation...

The ATLAS experiment at the LHC has measured the centrality dependence of charged particle pseudorapidity distributions over |η|<2 in lead-lead collisions at a nucleon-nucleon centre-of-mass energy of sNN=2.76 TeV. In order to include particles with transverse momentum as low as 30 MeV, the data were recorded with the central solenoid magnet off. C...

A search for the Higgs boson has been performed in the H→WW(*)→ℓ(+)νℓ(-)ν[over ¯] channel (ℓ=e/μ) with an integrated luminosity of 2.05 fb(-1) of pp collisions at √s=7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production...

A search for the standard model Higgs boson is performed in the diphoton decay channel. The data used correspond to an integrated luminosity of 4.9 fb(-1) collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of √s=7 TeV. In the diphoton mass range 110-150 GeV, the largest excess with...

A search for squarks and gluinos in final states containing high-p T jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in \( \sqrt{s}=8 \) TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3 fb−1. Results are interpreted...

A combined search for the Standard Model Higgs boson with the ATLAS experiment at the LHC using datasets corresponding to integrated luminosities from 1.04 fb-1 to 4.9 fb-1 of pp collisions collected at s=7 TeV is presented. The Higgs boson mass ranges 112.9-115.5 GeV, 131-238 GeV and 251-466 GeV are excluded at the 95% confidence level (CL), while...

A measurement of the ZZ production cross section in proton-proton collisions at sqrt[s] = 7 TeV using data corresponding to an integrated luminosity of 1.02 fb(-1) recorded by the ATLAS experiment at the LHC is presented. Twelve events containing two Z boson candidates decaying to electrons and/or muons are observed, with an expected background of...

A search for new phenomena in tt events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1.04 fb(-1) of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results...

The Beam Loss Monitoring System (BLM) of the Large Hadron Collider (LHC) is based on parallel plate Ionization Chambers (IC) with active volume 1.5l and a nitrogen filling gas at 0.1 bar overpressure. At the largest loss locations, the ICs generate signals large enough to saturate the read-out electronics. A reduction of the active volume and filli...

15 pages plus author list (27 pages total), 9 figures, 2 tables, submitted to Phys. Rev. D

This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at √s=7  TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21)  fb(-1) in the e(+)e(-) (μ(+)μ(-)) channel. No statistically significant excess...

A search for a Higgs boson has been performed in the H→WW→ℓνjj channel in 1.04 fb(-1) of pp collision data at √s=7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in th...

A search for pair-produced scalar particles decaying to a four-jet final state is presented. The analysis is performed using an integrated luminosity of 34pb−1 recorded by the ATLAS detector in 2010. No deviation from the Standard Model is observed. For a scalar mass of 100GeV (190GeV) the limit on the scalar gluon pair production cross section at...

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons ( b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt{s} = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb-1. The b-jets are identified using either a lifetime...

A search for a heavy standard model Higgs boson decaying via H→ZZ→→ℓ(+)ℓ(-)νν, where ℓ=e, μ, is presented. It is based on proton-proton collision data at √s=7 TeV, collected by the ATLAS experiment at the LHC in the first half of 2011 and corresponding to an integrated luminosity of 1.04 fb(-1). The data are compared to the expected standard model...

A measurement of the cross-section for ϒ(1S)→μμ production in proton-proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the ϒ(1S) transverse momentum in two bins of rapidity, |y|<1.2 and 1.2<|y|<2.4. The measurement requires that both muons have transverse momentum pTμ>4 GeV and pseudora...

A search for new phenomena in events featuring a high energy jet and large missing transverse momentum in proton-proton collisions at s = 7 TeV is presented using a dataset corresponding to an integrated luminosity of 33 pb -1 recorded with the ATLAS detector at the Large Hadron Collider. The number of observed events is consistent with the Standa...

The LHC Beam Loss Monitoring system (BLM) makes use of approximately 4000 detectors located around the 27 km ring. Its main purpose is to protect all critical elements of the LHC by requesting a beam abort when the measured losses exceed any of the predefined threshold levels. The BLM system integrates the acquired signals in 12 different continuou...

The jet fragmentation function and transverse profile for jets with 25GeV<p T jet<500GeV and |η jet|<1.2 produced in proton–proton collisions with a center-of-mass energy of 7TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb−1. Jets are reconstructed and their momentum measured using calorimetric info...

One of the major known limitations for the performance of the Large Hadron Collider are so called UFOs (Uniden-tified Falling Objects). UFOs were first observed in July 2010 and have since caused numerous protection beam dumps. UFOs are thought to be micrometer sized dust particles which lead to fast beam losses with a duration of about 10 turns wh...

A search for long-lived charged particles reaching the muon spectrometer is performed using a data sample of 37 pb - 1 from pp collisions at s = 7 TeV collected by the ATLAS detector at the LHC in 2010. No excess is observed above the estimated background. Stable τ ˜ sleptons are excluded at 95% CL up to a mass of 136 GeV , in GMSB models with N =...

The inclusive J/ψ production cross-section and fraction of J/ψ mesons produced in B-hadron decays are measured in proton-proton collisions at s=7 TeV with the ATLAS detector at the LHC, as a function of the transverse momentum and rapidity of the J/ψ, using 2.3 pb-1 of integrated luminosity. The cross-section is measured from a minimum p of 1 GeV t...

This Letter presents a measurement of the W+ W- production cross section in sqrt(s) = 7  TeV pp collisions by the ATLAS experiment, using 34  pb(-1) of integrated luminosity produced by the Large Hadron Collider at CERN. Selecting events with two isolated leptons, each either an electron or a muon, 8 candidate events are observed with an expected b...

A search for the Standard Model Higgs boson at the Large Hadron Collider (LHC) running at a centre-of-mass energy of 7TeV is reported, based on a total integrated luminosity of up to 40pb−1 collected by the ATLAS detector in 2010. Several Higgs boson decay channels: H→γγ, H→ZZ (∗)→ℓℓℓℓ, H→ZZ→ℓℓνν, H→ZZ→ℓℓqq, H→WW (∗)→ℓνℓν and H→WW→ℓνqq (ℓis e, μ) a...

Results are presented of searches for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons in Ös=7TeV\sqrt {s}=7~\mbox{TeV} proton–proton collisions at the Large Hadron Collider. Search strategies requiring lepton pairs with identical-sign or opposite-sign electric c...

Results are presented of a search for particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e, μ) of opposite charge in Ös=7\sqrt{s}=7TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour c...

A search for squarks and gluinos in final states containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded by the ATLAS experiment in sqrt(s) = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 35 inverse picobarns...

This Letter presents the first search for a heavy particle decaying into an e ± μ(-/+) final state in sqrt[s] = 7 TeV pp collisions at the LHC. The data were recorded by the ATLAS detector during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Exclusions at 95...