Power, pedagogy and participation: ethics and pragmatics in research with young people

This paper addresses issues of methodology when attempting to investigate the opinions of young people. It uses the concept of ‘ethical reflexivity’ (Gewirz & Cribb, 2006) to theorise some very practical considerations of research in classrooms. Drawing specifically on three studies of young people’s understandings of citizenship and their views on topical issues, two from England and one from Lebanon, we present ways in which the ethical challenges of such research can be met. Whilst acknowledging the power relationship between researchers and informants, we suggest that what we call ‘pedagogical research approaches’ built on a participative methodology can open up a space where both parties benefit. We argue that, when working in schools, we can take advantage of our status as teacher educators to present ourselves simultaneously as insiders and outsiders. We have devised what are intended to be non-exploitative research instruments that permit the gathering of useful qualitative data during a short encounter. We illustrate our approach with examples of classroom activities we have developed to provide simultaneously a valid learning experience and usable data

Performance of the CMS Level-1 trigger in proton-proton collisions at root s=13 TeV

At the start of Run 2 in 2015, the LHC delivered proton-proton collisions at a center-ofmass energy of 13 TeV. During Run 2 (years 2015-2018) the LHC eventually reached a luminosity of 2.1 x 10(34) cm(-2) s(-1), almost three times that reached during Run 1 (2009-2013) and a factor of two larger than the LHC design value, leading to events with up to a mean of about 50 simultaneous inelastic proton-proton collisions per bunch crossing (pileup). The CMS Level-1 trigger was upgraded prior to 2016 to improve the selection of physics events in the challenging conditions posed by the second run of the LHC. This paper describes the performance of the CMS Level-1 trigger upgrade during the data taking period of 2016-2018. The upgraded trigger implements pattern recognition and boosted decision tree regression techniques for muon reconstruction, includes pileup subtraction for jets and energy sums, and incorporates pileup-dependent isolation requirements for electrons and tau leptons. In addition, the new trigger calculates high-level quantities such as the invariant mass of pairs of reconstructed particles. The upgrade reduces the trigger rate from background processes and improves the trigger efficiency for a wide variety of physics signals

Correlations of azimuthal anisotropy Fourier harmonics with subevent cumulants in pPb collisions at root s(NN)=8.16 TeV

Event-by-event long-range correlations of azimuthal anisotropy Fourier coefficients (v(n)) in 8.16 TeV pPb data, collected by the CMS experiment at the CERN Large Hadron Collider, are extracted using a subevent four-particle cumulant technique applied to very low multiplicity events. Each combination of four charged particles is selected from either two, three, or four distinct subevent regions of a pseudorapidity range from -2.4 to 2.4 of the CMS tracker, and with transverse momentum between 0.3 and 3.0 GeV. Using the subevent cumulant technique, correlations between v(n) of different orders are measured as functions of particle multiplicity and compared to the standard cumulant method without subevents over a wide event multiplicity range. At high multiplicities, the v(2) and v(3) coefficients exhibit an anticorrelation; this behavior is observed consistently using various methods. The v(2) and v(4) correlation strength is found to depend on the number of subevents used in the calculation. As the event multiplicity decreases, the results from different subevent methods diverge because of different contributions of noncollective or few-particle correlations. Correlations extracted with the four-subevent method exhibit a tendency to diminish monotonically toward the lowest multiplicity region (about 20 charged tracks) investigated. These findings extend previous studies to a significantly lower event multiplicity range and establish the evidence for the onset of long-range collective multiparticle correlations in small system collisions

Measurement of the azimuthal anisotropy of Y(1S) and Y(2S) mesons in PbPb collisions at root s(NN)=5.02 TeV

The second-order Fourier coefficients (v(2)) characterizing the azimuthal distributions of Y(1S) and Y(2S) mesons produced in PbPb collisions at root s(NN) = 5.02 TeV are studied. The Y mesons are reconstructed in their dimuon decay channel, as measured by the CMS detector. The collected data set corresponds to an integrated luminosity of 1.7 nb(-1). The scalar product method is used to extract the v2 coefficients of the azimuthal distributions. Results are reported for the rapidity range vertical bar y vertical bar < 2.4, in the transverse momentum interval 0 < pT < 50 GeV/c, and in three centrality ranges of 10-30%, 30-50% and 50-90%. In contrast to the J/psi mesons, the measured v(2) values for the Y mesons are found to be consistent with zero. (C) 2021 The Author(s). Published by Elsevier B.V

OBSERVATION OF SHORT-RANGE 3-PARTICLE CORRELATIONS IN E(+)E(-) ANNIHILATIONS AT LEP ENERGIES

Measurements are presented of short range three-particle correlations in e(+)e(-) annihilations at LEP using data collected by the DELPHI detector. At small values of the four-momentum difference, strong three-particle correlations are observed for like-sign (+++ and —) and for unlike-sign (++- and +–) pion combinations which are not a consequence of two-particle correlations. A possible explanation of the observed effects in like-sign combinations is the existence of higher order Bose-Einstein interference, which significantly changes the particle distributions in jets

Search for excited leptons in e(+)e(-) collisions at root s=161 GeV

A search with the DELPHI detector at LEP for excited leptons (e*, mu*, tau* and nu*) decaying through gamma, W or Z transitions is reported. The data used correspond to an integrated luminosity of 10 pb(-1) e(+)e(-) centre-of-mass energy at an e of 161 GeV. The search for pair produced excited leptons established the limits m(e)* > 79.6 GeV/c(2), m(mu)* > 79.6 GeV/c(2), m(tau)* 79.4 GeV/c(2) and m(nu)* > 56.4 GeV/c(2) at 95% confidence level, assuming that the SU(2) and U(I) couplings of excited leptons are in the same ratio as for normal leptons and considering both left and right-handed components. Limits corresponding to other assumptions are also given. The search for single excited lepton production established upper limits on the ratio lambda/m(l)* of the coupling of the excited lepton to its mass

Measurement of the multiplicity of gluons splitting to bottom quark pairs in hadronic Z(0) decays

An inclusive measurement of the average multiplicity of b (b) over bar pairs from gluons, g(b (b) over bar), in hadronic Z(0) events collected by the DELPHI experiment at LEP, is presented. A counting technique, based on jet b-tagging in 4-jet events, has been used. Looking for secondary bottom production in events with production of any primary flavour, by requiring two b-tagged jets in well defined topological configurations, gave g(b (b) over bar) = (0.21 +/- 0.11(stat) +/- 0.09(syst))%. This result was checked with a different method designed to select events with four b quarks in the final state. Agreement within the errors was found. (C) 1997 Elsevier Science B.V