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Dorigo Cms Results.Pdf HEP-Chile 2016, Valparaiso Jan 7th New Results of the CMS Experiment Tommaso Dorigo INFN, Sezione di Padova Contents The CMS experiment and the 2015 run – The LHC and CMS – The Run 1 legacy – Preparations for Run 2 Standard model physics results – Toward the Higgs rediscovery – W, Z, top, B physics measurements New Physics searches – SUSY searches – Resonances, resonances, and more resonances – One much discussed candidate for 2016 Concluding remarks The CMS Collaboration 1700 physicists, 700 students, 950 engineers/technicians, 180 institutions from 43 countries 10k CPU cores, 2M lines of code The CMS Detector Muon system: Drift tubes (170k wires), RPC, Cathode Strip Ch.(200k wires) Silicon tracker: 66M pixel channels 9.6M strips, 210 m2 ECAL: 76k PbWO4 crystals HCAL: 15k scint/brass ch. The CMS Detector • CMS: A Compact Muon Solenoid • Actually much more than that: – a redundant, all-silicon tracking (210 m2) – a 4-Tesla solenoid for high-resolution momentum measurements – a Lead-tungstate crystal calorimeter for high- resolution EM shower measurements – hermetic hadron An all-purpose electronic eye for calorimetry subatomic physics – redundant muon coverage up to |η|<2.4 What to remember from Run 1 In Run 1 (2011-2012) the CMS experiment has published 447 articles based on data from 7- and 8- TeV pp collisions and heavy ion collisions This has resulted in the discovery of the Higgs boson, a new baryon, a few Y states, as well as in scores of other results, and notably the extension of lower limits on the mass of new particles and rate of rare new phenomena pp H ZZ* * New Ξb state New states in BJ/ψφ All CMS pubs: http://cms-results.web.cern.ch/cms-results/public-results/publications/ Run 2 data: 13 TeV collisions CMS Preliminary Recorded @ 3.8 T = 2.8 fb-1 Good for all: 2.2 fb-1 Good for many*: 2.6 fb-1 Good for muons: 2.7 fb-1 Preliminary luminosity uncertainty: 4.8% @ 50 ns 4.6% @ 25ns * |h| < 3.0 for jets and MET A feel-good graph - dimuon resonances CMS-DP-2015/055 Standard Model measurements at 13 TeV Inclusive jet cross section The inclusive jet production cross section has been measured in bins of jet pT and h using 72/pb of 13 TeV data A good agreement with QCD predictions using improved tuning of NP and hadronization is observed with both cone radii used (0.4 below, and 0.7, right) NLOJET++ POWHEG+PYTHIA8 SMP-15-007 B meson production B cross sections are studied as a function of pT and y and compared to FONLL predictions Use standard B+J/ψK decay from dimuon trigger Good agreement with theory is observed in the investigated range up to pT 100 GeV BPH-15-004 W and Z production • The first 43/pb of 13 TeV data allowed measurements of inclusive W and Z cross sections and their ratios (W/Z, W+/W-) • A new measurement of Z(μμ) +jets differential cross sections has also been produced with 2.5/fb of Run 2 data SMP-15-004 SMP-15-010 Diboson production: ZZ, WZ Dibosons provide a further check of the SM at the higher energy of the 2015 run Boson pairs are a background to many NP searches (including Higgs production) 1.3/fb of Run 2 data were used for these measurements Data and SM predictions are in very good agreement. The measurements are: pp WZ lnl’l’ pp ZZ 4lep SMP-15-005 SMP-15-006 Top quark production cross sections • Top is mainly produced in pairs by gluon-gluon collisions; also produced singly via EW processes (W*tb, bgtW, gWtbq) • Top pairs mainly undergo three possible decay modes: dileptonic (e,μ: 5%), single lepton (e,μ+jets: 30%), hadronic (all jets: 45%); these have complementary issues and purity • The precision of CMS results challenges NNLO+NNLL QCD calculations Bottom line: Great agreement! This is a true success of precision calculations of perturbative QCD Single top quark production The t-channel production of single top occurs in pp collisions via two different processes, one of which is sensitive to the b-quark content of the proton CMS has measured t-channel production in a fiducial PS region, finding good agreement with both aMC & POWHEG TOP-15-004 Underlying event: now studied in tt events The study seeks to improve the event modeling in 푡푡 production, using fully reconstructed single lepton events CMS measures charged particle activity (N, ΣpT, <pT>) in different regions relative to the momentum of the 푡푡 system, as a function of pT(푡푡) and for different jet multiplicities Left: charged multiplicity compared to models with (2Q)2 scale for fragmentation and renormalization Right: Δφ distributions The models describe the data reasonably well within model systematics, so it appears not necessary to have a different UE tune to describe heavy flavour TOP-15-017 production Standard Model Summary CMS Higgs boson results (Run 1) • Mass: MH=125.00 ± 0.27 ± 0.15 GeV • Cross section: +0.08 μ = 1.00 ± 0.09 (stat) −0.07 (theo) ± 0.07 (syst) • JP: O+ • Couplings: As the SM predicts! Left: fits to the signal strength μ from measurements in different final states allow to disentangle the contribution of different production modes Right: coupling of Higgs boson to different particles is compared to SM predictions Higgs physics at 13 TeV Higgs production by gluon-gluon fusion and VBF processes increase by a factor of 2.6 with respect to 8 TeV Discovery channels visible with 5 fb-1 ttH production is boosted by factor x4 Going after Hbb observation soon Preliminary studies of analysis-level inputs, control regions, measurements of trigger, ID, selection efficiencies in kinematic regions relevant for Higgs physics The new energy and running conditions impose reoptimization and retuning preliminary studies done with few /fb of data, ready for opening the box (so far signal regions kept blinded to avoid biasing ourselves) Kinematic discriminant Higgs studies: ZZ(4l) for m > 150 GeV 4l Discriminant vs. m4l Above: m4l mass with Higgs region blinded, using 2.6/fb of 13 TeV data New Physics Searches 13 TeV: increased reach for high-mass objects 13 TeV with 2.2 fb-1 potentially more sensitive than 8 TeV (19.8 fb-1) CMS SUSY Searches CMS is very active in SUSY searches, as we are a bunch of crazy dreamers. However, we have not found sparticles yet. As a justification I can offer the following: it is quite hard to find a black cat in a dark room, especially if there is no cat We have produced only a string of lower limits on particle masses so far. Still, it is an exciting business - but there is no time to cover the topic here. Only flashing a couple of results in the next few slides – a check of an interesting excess of Run 1, and a summary of gluino searches SUSY in opposite-sign dileptons The Run 1 analyses of this channel revealed some deviations from SM backgrounds With off-Z-peak lepton pairs CMS saw a 2.6σ excess in Run 1, but no similar excess was seen in ATLAS data OTOH, In Z-like events ATLAS observed a 3.0σ excess in the high-HT region, while CMS saw no excess Run 2 data was needed to clarify the situation ! Opposite-sign dileptons at 13 TeV • The search has been repeated using 2.2/fb of Run 2 data at 13 TeV • The off-peak selection is similar to Run 1; the on-peak analysis is divided in 12 search regions, and also includes a region targeting the ATLAS excess • No significant signals are observed: – Upper limits are below predicted yields scaling from the Run 1 excesses Run 1 Left: the region excess where CMS saw an off-peak excess in Run 1 Right: the search region targeting the Run 1 ATLAS excess As ATLAS continues to see it, something is fishy SUS-15-011 Gluino searches: overview Multiple complementary final states and • Inclusive searches approaches have been investigated: benchmarked with • 0 leptons simplified models – MHT, HT (SUS-15-002) – MT2 (SUS-15-003) – Razor (SUS-15-004) – aT (SUS-15-005) • 1 lepton – Sum of jet masses MJ (SUS-15-007) – Razor (SUS-15-004) • Same-sign dilepton (SUS-15-008) – Rare SM signature Run 1: limits range up to 1.4 TeV Large σ boost at 13 TeV! Gluino search results Executive summary: no significant signals observed Exclusions reach to > 1.7 TeV for simplified models, at low LSP mass These results significantly exceed Run 1 limits Run 1 exclusion thanks to the sqrt(s) increase Run 1 exclusion Run 1 exclusion Going deeper into the implausible If your trust that the LHC will find new physics is strong, you certainly approve to casting the net in the open sea even without a real idea of what fish you could be catching, nor a gauge to assess critically the results The attitude of taking any departure from model predictions as a potential signal of new physics is not dangerous per se, but it can divert the attention from more principled searches and studies – one example is given later I believe we also need to explain to the users of our physics results that a "global p-value" is still not a p-value! With that in mind, let us give a look at the catch of 2015 Search for diboson resonances • In Run 1 CMS saw a 2s excess near 1.8-2.0 TeV; ATLAS had a >3 sigma effect in similar mass region • Repeated search at 13 TeV using most sensitive channels: lnJ, JJ • Analysis categorized in dijet mass for optimal sensitivity to WW, WZ, ZZ signals • 13 TeV: no excess observed in the region of interest near 2 TeV – More data needed to fully exclude Run 1 excess … but of course this is one signal close to be dumped GBulkWW (lνJ+JJ) W’WZ (lνJ+JJ) GBulkZZ (JJ) EXO-15-002 B2G-15-004 Search for 푊′ → ln or tb EXO-15-006 • A search was done for heavy gauge boson W’ decaying to leptons+missing transverse energy or tb in the lepton+jets channel • Mass exclusions: < 4.4 TeV in lep+MET, < 2.38 TeV tb (Run 1 limits 2-3 TeV) 푾′ → tb 푾′ → ln Search for dijet resonances A bump hunt has been carried out on the smoothly falling background of mjj , testing s- channel production of new heavy resonances Highest mass dijet pair observed: 6.14 TeV New physics searches in dijets CMS searched for new physics in the dijet angular distribution, using 95% CL Limits: Contact int.
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