Longitudinal density monitor for the LHC

Jeff, Adam; Andersen, Marianne; Boccardi, Andrea; Bozyigit, S.; Bravin, E.; Lefèvre, T.; Rabiller, A.; Roncarolo, Federico; Welsch, Carsten; Fisher, Alan

doi:10.1103/physrevstab.15.032803

Cited by 12 publications

(11 citation statements)

References 11 publications

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“…The charge in the other nine RF buckets of the BCID is not seen. Data from the Longitudinal Density Monitors of the LHC indicate that the ghost charge is quite uniformly distributed in all RF buckets of a non-colliding BCID [31,32]. Figure 12 shows a summary of BCM collision-like and background-like trigger rates for a particularly interesting BCID range of a bunch pattern with 1317 colliding bunches.…”

Section: Jinst 8 P07004mentioning

confidence: 99%

Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run

Aad¹,

Kupčo²,

Samset³

et al. 2013

J. Inst.

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This paper presents a summary of beam-induced backgrounds observed in the ATLAS detector and discusses methods to tag and remove background contaminated events in data. Triggerrate based monitoring of beam-related backgrounds is presented. The correlations of backgrounds with machine conditions, such as residual pressure in the beam-pipe, are discussed. Results from dedicated beam-background simulations are shown, and their qualitative agreement with data is evaluated. Data taken during the passage of unpaired, i.e. non-colliding, proton bunches is used to obtain background-enriched data samples. These are used to identify characteristic features of beam-induced backgrounds, which then are exploited to develop dedicated background tagging tools. These tools, based on observables in the Pixel detector, the muon spectrometer and the calorimeters, are described in detail and their efficiencies are evaluated. Finally an example of an application of these techniques to a monojet analysis is given, which demonstrates the importance of such event cleaning techniques for some new physics searches.

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Section: Jinst 8 P07004mentioning

confidence: 99%

Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run

Aad¹,

Kupčo²,

Samset³

et al. 2013

J. Inst.

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“…The total beam intensities are measured with the DC current transformers (DCCT) [35], and the bunch currents measured with the fast beam current transformers (FBCT) [36], and cross-checked with the longitudinal density monitors (LDMs) [37,38] and the beam quality monitors [39]. Because of the low beam intensity and low collision rate, the luminosity remains nearly constant over the course of time, in contrast to typical physics fills [9].…”

Section: Analysis Of Vdm Scan Datamentioning

confidence: 99%

Precision luminosity measurement in proton–proton collisions at $$\sqrt{s} = 13\,\hbox {TeV}$$ in 2015 and 2016 at CMS

et al. 2021

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The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton–proton collisions at $$\sqrt{s}=13\,{\text {TeV}} $$ s = 13 TeV in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 $$\,\text {fb}^{-1}$$ fb - 1 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.

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“…It is operationally measured by the LHC beam quality monitor (BQM) [57] which uses a wall current monitor pick-up (WCM) [58] to acquire the longitudinal profiles. Additionally, the longitudinal synchrotron radiation monitor (BSRL) [59], which uses the same synchrotron light source as the BSRT, continuously measures the longitudinal distribution of charges in the beams. The scopes connected to the WCM pick-ups can acquire longitudinal bunch profiles of both beams during a full LHC cycle.…”

Section: Bunch Profile Measurements In the Lhcmentioning

confidence: 99%

Impact of non-Gaussian beam profiles in the performance of hadron colliders

Papadopoulou

Antoniou

Argyropoulos

et al. 2020

Phys. Rev. Accel. Beams

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At the Large Hadron Collider (LHC), the interplay between a series of effects, including intrabeam scattering (IBS), synchrotron radiation, longitudinal beam manipulations, two beam effects (beam-beam, e-cloud) and machine nonlinearities, can change the population of the core and tails and lead to non-Gaussian beam distributions, at different periods during the beam cycle. By employing generalized distribution functions, it can be demonstrated that the modified non-Gaussian beam profiles have an impact in the beam emittance evolution by itself and thereby to the collider luminosity. This paper focuses on the estimation of beam distribution modification and the resulting rms beam size due to the combined effect of IBS and synchrotron radiation by employing a Monte-Carlo simulation code which is able to track 3D generalized particle distributions (SIRE). The code is first benchmarked over classical semianalytical IBS theories and then compared with measurements from the LHC at injection and collision energies, including projections for the High-Luminosity LHC (HL-LHC) high brightness regime. The impact of the distribution shape on the evolution of the bunch characteristics and machine performance is finally addressed.

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Longitudinal density monitor for the LHC

Cited by 12 publications

References 11 publications

Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run

Characterisation and mitigation of beam-induced backgrounds observed in the ATLAS detector during the 2011 proton-proton run

Precision luminosity measurement in proton–proton collisions at $$\sqrt{s} = 13\,\hbox {TeV}$$ in 2015 and 2016 at CMS

Impact of non-Gaussian beam profiles in the performance of hadron colliders

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