responding to colors that quarks possess. The requirement of local gauge invariance under this symmetry requires the existence of 8 massless gauge bosons, the gluons. Gluons also have color, thus gluons can also interact with themselves. Gluon-gluon interactions contribute to two phenomenologically important properties of the strong force. The first is asymptotic freedom - as the energy scale of the interaction increases the coupling constant becomes small. This property allows for perturbative calcu- lation to be made for strong interactions at high energies . The second is quark confinement - the force between quarks increases with distance, leaving quarks either bound together, or through quark-antiquark pair creation resulting in two separate hadrons . That explains the absence of free quarks and the formation of mesons and hadrons which are color-neutral combinations of quarks.
Many physical scenarios outside the framework of the SM predict the existence of new resonance states in the spectra of the SM particles . For example, heavy (with a mass of several TeV) resonances in the spectrum of pairs of leptons and jets appear in four-dimensional models with an extended gauge sector (extra gauge boson Z beyond the SM with spin S = 1). In its characteristics,
A search is performed for the first time for neutralresonances above the Higgs boson mass pro- duced by the qq → Rqq → ` + ν ` − ν ¯ qq (` = e, µ) fusion process, taking into account interference with the SM production process of the same final state. A representative Feynman diagram of the production and decay of the resonance is shown in Figure 1. Only leptonic channels are considered in view of the relatively small SM backgrounds expected. Three channels are labeled based on the lepton flavors: ee, eµ, and µµ. The analysis is based on an integrated luminosity of 3.2 fb −1 of proton-proton collision data taken at √ s = 13 TeV with the ATLAS detector at the LHC in 2015. The method and results of this analysis are referenced from this ATLAS conference note .
π 0 and to improve the resolution of the shower position and di- rection measurements. In the region | η | < 1 . 8, the electromagnetic calorimeter is preceded by a presampler detector to correct for upstream energy losses. An iron-scintillator/tile calorimeter gives hadronic coverage in the central rapidity range ( | η | < 1 . 7), while a LAr hadronic end-cap calorimeter provides coverage over 1 . 5 < | η | < 3 . 2. The forward regions (3 . 2 < | η | < 4 . 9) are instrumented with LAr calorimeters for both electromagnetic and hadronic mea- surements. The muon spectrometer (MS) surrounds the calorime- ters and consists of three large air-core superconducting magnets providing a toroidal ﬁeld, each with eight coils, a system of pre- cision tracking chambers, and fast detectors for triggering. The combination of all these systems provides charged particle mea- surements together with eﬃcient and precise lepton and photon measurements in the pseudorapidity range | η | < 2 . 5. Jets and E miss T are reconstructed using energy deposits over the full coverage of the calorimeters, | η | < 4 . 9.
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 p ﬃﬃﬃ s ¼ 7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 ð1 : 21Þ fb 1 in the e þ e ( þ ) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C.L. on the cross section times branching fraction of Z 0 resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z 0 boson is set. A Randall-Sundrum graviton with coupling k= M Pl ¼ 0 : 1 is
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC, and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST, and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR, and VSC CR, Czech Republic; DNRF, DNSRC, and Lundbeck Foundation, Denmark; ARTEMIS, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNAS, Georgia; BMBF, DFG, HGF, MPG, and AvH Foundation, Germany; GSRT, Greece; ISF, MINERVA, GIF, DIP, and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW, Poland; GRICES and FCT, Portugal; MERYS (MECTS), Romania; MES of Russia and ROSATOM, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and MVZT, Slovenia; DST/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF, and Cantons of Bern and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society, and Leverhulme Trust, United Kingdom; DOE and NSF, U.S. The crucial computing support from all WLCG partners is acknowl- edged gratefully, in particular, from CERN and the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden),CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK), and BNL (U.S.), and in the Tier-2 facilities worldwide.
Two searches for a heavy H → ZZ → qq/ννqq and CP-odd A → Zh → bb/ννbb were performed owing to improved dijet mass resolution which used both the calorimeter and tracking information. The searches looked for either a pair of same-flavour opposite charge isolated leptons or large missing transverse energy together with either a merged fat jet (R = 1.0) or a pair of narrow jets (R = 0.4). The merged and resolved candidates were looked for sequentially, covering a large range of heavy resonance mass hypothesis. In the H → ZZ search, the candidates were categorised as ggF or VBF in the presence of additional two forward jets with high ∆η j j and high m j j . The search
first consider the flux of standard light neutrinos com- ing from kaon decays in the beamline and crossing the ND280 TPCs. This flux is transformed into a flux of heavy neutrinos (K ± → ` ± α N , α = e, µ) by weight- ing event-by-event using the appropriate branching ra- tios  and modified kinematics. The analysis as- sumes the heavy neutrino lifetime is long enough to reach ND280 (τ 1 µs), which is consistent with current lim- its on the mixing elements. Figure 2 presents the results of the simulation for different heavy neutrino masses and for both production modes in neutrino mode. The flux has the same shape for anti-neutrino mode, although it is a factor of ∼ 3 lower.
The Compact Muon Solenoid (CMS) is one of two general purpose detectors at the LHC. The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter, providing an axial magnetic field of 3.8 T. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Muons are measured in gas-ionization detectors embedded in the steel flux-return yoke outside the solenoid. Extensive forward calorimetry complements the coverage provided by the barrel and endcap detectors. The CMS experiment has been designed with a two-level trigger system, the Level-1 Trigger (L1), implemented in custom- designed electronics, and the High Level Trigger (HLT), a streamlined version of the CMS o ffl ine reconstruction software running on a computer farm. A more detailed description of the CMSdetector, together with a definition of the coordinate system used and the relevant kinematic variables, can be found in Ref . During LHC Run 2, which started in 2015 and will continue through 2018, proton- proton collisions are produced at centre-of-mass energies of 13 TeV with 25 ns bunch spacing. This resulted in nearly 60 fb −1 of integrated luminosity delivered to CMS from 2015 until mid-August
The Compact Muon Solenoid (CMS) detector is a multipurpose detector designed for discovery searches at the LHC . The main motivation of the LHC is to elu- cidate the nature of electroweak symmetry breaking, presumed to be via the Higgs mechanism. The study of the Higgs mechanism can also test the consistency of the Standard Model above ∼ 1 TeV. Additionally, there are hopes for other discoveries that could lead toward a unified theory of physics. These discoveries could manifest themselves as supersymmetry, or modifications to gravity at the TeV scale through extra dimensions. These are a few of the many reasons to investigate the TeV scale. A hadron collider is well suited to provide the center-of-mass energy and luminosity needed to study these rare processes. However, the 7-fold energy increase and 100-fold luminosity increase over previous hadron colliders leads to experimental challenges as well. At √ s = 14 TeV the cross section for proton-proton interactions would yield 10 9 interactions/s at design luminosity, which must be reduced by the trigger system
Since the ATLAS detector identiﬁes leptons with large trans- verse momenta with high purity, eﬃciently, and with good mo- mentum resolution, it is well suited to a search for this signature. Many new physics models allow LFV in charged lepton interac- tions. For example, in R-parity-violating (RPV) models of super- symmetry (SUSY) , a sneutrino can have LFV decays to . Models with additional gauge symmetry can accommodate an signature through LFV decays of an extra gauge boson Z . This signature is also produced in the SM framework, for example, t t, ¯ W W , or Z / γ ∗ → τ − τ + production where the ﬁnal-state particles decay to leptons of different ﬂavour. These processes typically have small cross sections for pairs with invariant mass (m ) in the high-mass range not already excluded for new physics signals.
LHC data is being used to seek evidence of 2 → 2 scattering processes where a narrow resonance arising from physics Beyond the Standard Model (BSM) is produced in the s-channel and immediately decays to visible final state particles. Experiment is often compared with theory by showing how a few benchmark models with specific parameter choices compare to the observed limits on the cross-section (σ) times branching fraction (BR) for the process. Yet at the beginning of the analysis, especially when a small excess may be present, it would be invaluable to compare the data with entire classes of models, to immediately pare down the list of relevant options. This work builds o ff of our previous results on identifying the color [1, 2] and spin  properties of new discovered resonances decaying to dijet final states. We have extended these ideas to a wider variety of final states and to situations in which just a small deviation possibly indicative of a resonance has been observed.
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, HGF and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute
Abstract. The CMS experiment at the LHC collected in 2011 around 5 /fb of integrated luminosity at 7 TeV center-of-mass energy. The CMSdetector has shown an excellent data taking eﬃciency. The global CMS and several subdetector performances will be pre- sented. The goal of the 2012 operations is to collect again 5 /fb by the end of June and ﬁnally more than 15 /fb at the end of 2012, with a new center-of-mass energy at 8 TeV and higher luminosity. The CMSdetector should cope with these new conditions and the ﬁrst results from 2012 data will be given.
We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.
An extensive list of forward physics measurements performed with data taken in 2015 at p s = 13 TeV is presented. The measurements presented here can be used as input for tuning of existing hadronic interaction models. The collection of measurements in the forward region is an important baseline for more exclusive analyses and shows that forward physics is well understood within the systematic uncertainties at a p s = 13 TeV scale collected by CMS.
with 10% precision. The first physics run started in 2016, after a period of detectors commissioning. The proton beam extracted from the SPS is used to generate a sec- ondary hadron beam selected in charge (positive) and mo- mentum (75 GeV/c) through a system of dipoles and col- limators. The nominal intensity is of 750 MHz, but only a small fraction of the hadrons in the beam are kaons (about ∼ 6%). The kaons are positively identified by a Cherenkov beam detector (KTAG). The momentum of each particle in the beam is measured by a beam spectrometer com- posed by three stations of silicon pixels detector (Giga- tracker) exposed at full intensity. An about 150 m long decay region is followed by a straw tubes spectrometer in vacuum in order to minimize the material present along the path of the photons produced in kaon decays (mainly K + → π + π 0 ). These photons are detected by the LKr calorimeter and a system of vetoes placed along the fidu- cial volume (12 rings of lead glass) and around the beam direction. The photon veto system guarantees a coverage up to 50 mrad. The particle identification is done by using a Ring Imaging Cherenkov (RICH), electromagnetic and hadronic calorimeters, and Muon Veto (MUV). A detailed description of the NA62 beam line and detectors can be found in .
Abstract. One of the main targets of the CMS experiment is to search for the Standard Model Higgs boson. The 4-lepton channel (from the decay H → ZZ → 4l, l = e, μ) is one of the most promising. The analysis is based on the identiﬁcation of two opposite-sign, same-ﬂavor lepton pairs: leptons are required to be isolated and to come from the same primary vertex. The Higgs would be statistically revealed by the presence of a resonance peak in the 4-lepton invariant mass distribution. The Higgs mass is a free parameter of the Standard Model, and the 4-lepton channelsearch is sensitive almost in the entire mass range. With data collected in 2010 and 2011 (4.7 fb − 1 at √ s = 7 TeV) the Higgs boson
institutes for their contributions to the success of the CMS e↵ort. We gratefully acknowledge the computing centres and personnel of the Worldwide LHC Computing Grid for delivering the com- puting infrastructure essential to our analyses. Finally, we ac- knowledge the enduring support for the construction and opera- tion of the LHC and the CMSdetector provided by the following funding agencies: BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COL- CIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Republic of Korea); LAS (Lithua- nia); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mex- ico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United King- dom); DOE and NSF (USA).
A search is performed for resonant W W , W Z or ZZ production in final states with at least one hadronically decaying vector boson, using 3.2 fb −1 of proton-proton collisions at √ s = 13 TeV recorded in 2015 by the ATLAS detector at the LHC. No significant excesses are found in data compared to the SM predictions. Limits on the production cross-section times branching ratio into vector-boson pairs are obtained as a function of the resonance mass for resonances arising from a model predicting the existence of a new heavy scalar singlet, from a simplified model predicting a heavy vector-boson triplet, or from a bulk Randall-Sundrum model with a heavy spin-2 graviton. A scalar resonance with mass below 2650 GeV predicted by the Unsuppressed model, a heavy vector-boson triplet predicted by model-B with g v = 3 of the HVT parameterisation with mass below