Transverse Energy Events Research Articles

Signature-based search for delayed photons in exclusive photon plus missing transverse energy events frompp¯collisions withs=1.96 TeV

We present the first signature-based search for delayed photons using an exclusive photon plus missing transverse energy final state. Events are reconstructed in a data sample from the CDF II detector corresponding to $6.3 \text{fb}^{-1}$ of integrated luminosity from $\sqrt{s}=1.96$ TeV proton-antiproton collisions. Candidate events are selected if they contain a photon with an arrival time in the detector larger than expected from a promptly-produced photon. The mean number of events from standard model sources predicted by the data-driven background model based on the photon timing distribution is $286 \pm 24$. A total of 322 events are observed. A $p$-value of 12% is obtained, showing consistency of the data with standard model predictions.

Comprehensive constraints on a spin-3/2 singlet particle as a dark matter candidate

We consider the proposal that dark matter (DM) is composed of aspin-3/2 Dirac-type particle that is a singlet of the standard model(SM). Its leading effective interactions with ordinary matterinvolve a pair of their fields and a pair of SM fermions, in theform of products of chiral currents. We make a comprehensiveanalysis on possible phenomenological effects of the interactions invarious experiments and observations. These include collidersearches for monojet plus missing transverse energy events, directdetections of DM scattering off nuclei, possible impacts on thegamma rays and antiproton-to-proton flux ratio in cosmic rays, andthe observed relic density. The current data already set strongconstraints on the effective interactions in a complementary manner.The constraint from collider searches is most effective at arelatively low mass of DM, and the antiproton-to-proton flux ratiooffers the best bound for a heavy DM, while the spin-independentdirect detection is the best in between. Putting all constraintstogether, a DM mass less than ∼ 1TeV has been excluded,leaving behind a small window for a heavy DM particle of spin-3/2.

Triplet scalars and dark matter at the LHC

We investigate the predictions of a simple extension of the standard model where the Higgs sector is composed of one $\mathrm{SU}(2{)}_{L}$ doublet and one real triplet. We discuss the general features of the model, including its vacuum structure, theoretical and phenomenological constraints, and expectations for Higgs collider studies. The model predicts the existence of a pair of light charged scalars and, for vanishing triplet vacuum expectation value, contains a cold dark matter candidate. When the latter possibility occurs, the charged scalars are long-lived, leading to a prediction of distinctive single charged track with missing transverse energy or double charged track events at the large hadron collider. The model predicts a significant excess of two-photon events compared to SM expectations due to the presence of a light charged scalar.

Search for Heavy Long-Lived Particles that Decay to Photons at CDF II

We present the first search for heavy, long-lived particles that decay to photons at a hadron collider. We use a sample of gamma + jet + missing transverse energy events in pp[over] collisions at square root[s] = 1.96 TeV taken with the CDF II detector. Candidate events are selected based on the arrival time of the photon at the detector. Using an integrated luminosity of 570 pb(-1) of collision data, we observe 2 events, consistent with the background estimate of 1.3+/-0.7 events. While our search strategy does not rely on model-specific dynamics, we set cross section limits in a supersymmetric model with [Formula: see text] and place the world-best 95% C.L. lower limit on the [Formula: see text] mass of 101 GeV/c(2) at [Formula: see text].

The shape of dilepton spectra in heavy ion collisions as a signature of quark-gluon plasma

The formation of quark-gluon plasma in heavy ion collisions should manifest itself by the increase of the ratio of medium to large mass dileptons, the former being produced predominantly in the QGP and the mixed phase whereas the latter are produced mostly by the Drell-Yan process. The increase of this ratio should be visible either when comparing collisions of lighter with heavier ions, e.g. O+O with Pb+Pb or when comparing low and large transverse energy events in heavy ion e.g. Pb+Pb collisions.

Transverse energy measurements in proton-nucleus interactions at high energy

The results of two sets of transverse energy measurements, performed with incident proton beams of 200 and 450 GeV/c momentum on several nuclear targets, are presented. The transverse energy cross sections dσ/dET are measured in a pseudorapidity range including the target fragmentation region (−0.1<η<2.9) for both data sets and also in a nearly complete pseudorapidity coverage (−0.1<η<5.5) for the data taken at 200 GeV/c incident momentum. A comparison is made of the transverse energy distributions in the target fragmentation region and in the full η region. We find that the mean value of pseudorapidity of the dET/dη distributions shifts towards the target fragmentation region as the atomic mass number of the target increases or a selection of high transverse energy events is made. A parametrization based on a simple geometrical nucleonnucleon scattering approach was found to be inadequate to describe all features of the transverse energy distributions. Finally, the VENUS model is compared with the experimental data.

The possibility to observe QCD instanton

If, at high energies, the QCD-instanton-induced cross section reaches its unitarity limit, this process should be considered as the main source of the large transverse energy events. The events of such a type should be observed already at Sp p S or FNAL colliders in the range of E T>100–200 GeV. However, if the emission of a large number of gluons compensates no more than one half of the exponential suppression of the instanton amplitude, it will be not so easy (but at E T∼30 GeV still hopeful) to select the events induced by the QCD instantons.

An on-line trigger processor for large transverse energy events

A trigger processor for the selection of events in which photons of large transverse momentum are detected by a lead and scintillating glass calorimeter was designed, constructed, and operated at interaction rates ranging from 2 kHz to 2 MHz. The system achieved suppressions of the raw interaction rate of as much as 1*10/sup -5/. Raw distributions of transverse momenta and direct photon event sensitivities are presented for data taken with 300-GeV/c pion and proton beams on a lithium target.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the anomalous large transverse energy events observed in proton-lead scattering

It has been shown that a study of correlation between the average rapidity, 〈y〉, and transverse energy,E T , can be used to distinguish between different origins of large transverse energy events observed inp-Pb scattering in the HELIOS experiment. If the largeE T events are to be attributed to a nuclear dependence of structure functions then the hard scattering picture implies a positive correlation among the above two quantities, contrary to that seen in experiment.

Missing Transverse Energy Events and a Search for Additional Neutrino Families and a Fourth‐Generation Lepton

Annals of the New York Academy of SciencesVolume 518, Issue 1 p. 9-18 Missing Transverse Energy Events and a Search for Additional Neutrino Families and a Fourth-Generation Lepton MISSING ENERGY EVENTS IN UA1 DAVID B. CLINE, DAVID B. CLINE Department of Physics University of California Los Angeles, California 90024Search for more papers by this author DAVID B. CLINE, DAVID B. CLINE Department of Physics University of California Los Angeles, California 90024Search for more papers by this author First published: December 1987 https://doi.org/10.1111/j.1749-6632.1987.tb48802.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume518, Issue1The Fourth Family of Quarks and Leptons: First International SymposiumDecember 1987Pages 9-18 RelatedInformation

Analysis of the highest transverse energy events seen in the UA 1 detector at the $$Sp\bar pS$$ collider

This is the first full solid angle analysis of large transverse energy events in\(p\bar p\) collisions at the CERN collider. Events with transverse energies in excess of 200 GeV at\(\sqrt s = 630 GeV\) are studied for any non-standard physics and quantitatively compared with expectations from perturbative QCD Monte Carlo models. A corrected differential cross section is presented. A detailed examination is made of jet profiles, event jet multiplicities and the fraction of the transverse energy carried by the two jets with the highest transverse jet energies. There is good agreement with standard theory for events with transverse energies up to the largest observed values\(( \approx \sqrt {s/2} )\) and the analysis shows no evidence for any non-QCD mechanism to account for the event characteristics.

Events with large missing transverse energy at the cern collider: II. search for the decays of W ± into heavy leptons and of Z 0 into non-interacting particles

We report on further analysis of events with large missing transverse energy from 715 nb −1 of data from the UA1 experiment at the CERN proton-antiproton collider. Measured W and Z 0 rates and heavy flavour cross sections are used to predict rates of missing transverse energy event from all known standard model process. Limits are derived on two possible new sources, namely: (1) semi-hadronic decays of a fourth sequential charged heavy lepton coupling to the W boson, (2) Z 0 decays into additional pairs of non-interacting particles. After taking into additional pairs of non-interacting particles. After taking into account all known sources of missing transverse energy events, we find a mass limit on a fourth-generation charged lepton of m L>41 GeV/ c 2 (90% CL) and a limit on the number of additional neutrino species of n⩽7 (90% CL).

On the squark and gluino mass limits from the CERN pp̄ collider

Recently announced lower limits on squark and gluino masses from CERN pp̄ collider data depend on three assumptions: (1) that the photino (γ) is the lightest supersymmetric particle and escapes experimental detection, (2) that m γ ≅ 0, and (3) that the five contributing flavors of right and left squars are mass degenerate. We examine the effect of relaxing these conditions on the quoted mass limits. We find the squark (gluino) mass limit virtually insensitive to increases in photino mass up to mγ ∼ 30–40 GeV (20–30 GeV) if all jet + missing transverse energy (p T) events are taken into account. Furthermore, we quantify the effect of an unstable γ scenario on both q̃ and g̃ mass limits. Finally we find that by relaxing the assumption of squark mass degeneracy, some squarks with masses as much as 10–15 GeV below quoted bounds may be compatible with the data.

Higgs-hyperfermion interaction and large missing transverse energy events

A strong Higgs-hyperfermion interaction in a two-Higgs-doublet model is introduced to explain the large missing transverse energy events. τ τ decaying from a high energy Higgs explain the monojet activity and bb̄ from another Higgs describe the two-jet activity. The ARGUS and the Crystal Ball experiments for the radiative decay constrain the monojet rate.

High transverse energy and high transverse momentum events in [formula omitted] and pp interactions at the CERN intersecting storage rings

A comparison between p p and pp interactions at √ s = 52.7 GeV is presented for a total neutral transverse energy ( E T o ) trigger and for a high transverse momentum ( p T) neutral cluster trigger. The rate of production of events in the range 6< E T o <20 GeV is observed to be 10% higher in p p collisions than in pp collisions. A study of the structure of the events shows this excess to be due to more isotropic events being produced in p p collisions. The ratio of the production cross section for single neutral clusters in p p and pp interactions in the range 1.25< p T<10 GeV/ c does not significantly differ from unity.

Missing transverse energy events and the standard model

The processes p+ p → W ± , Z 0+0,1,2 jets are studied in the light of recent observations of events with large missing transverse momentum at the CERN p p collider. We find that a nontrivial number of such events can arise from the leptonic decays Z 0 → ν ν and W ± → ℓ ± ν where the charged lepton escapes identification. In both cases the number of events with one jet and with two jets are comparable. By correlating these decay modes with those where the leptons are observed we can, in principle, eliminate the theoretical uncertainties inherent in such perturbative QCD calculations.

Jets in high transverse energy events at the CERN intersecting storage rings

Most events with high neutral transverse energy, E T 0, produced in pp colisions at √ s = 62.3 GeV, are jet-like. The evidence for this is presented, based on data collected using an electromagnetic calorimeter covering 90% of 2π in azimuth. The spectrum d N/d E T 0 has been measured over the E T 0 range from 10 to 35 GeV. Properties of the observed jets are discussed.

Observation of jet structure in high transverse energy events at the CERN intersecting storage rings

The spectrum dN dE T 0 ( E T 0 = neutral transverse energy) has been measured with an electromagnetic calorimeter covering 90% of 2 π in azimuth. The measurement, performed in pp collisions at s = 62 GeV , covered the E T 0 range from 10 to 30 GeV. Evidence is presented that a large fraction of these events are jet-like, the fraction increasing with E T 0.

Observation of jets in high transverse energy events at the CERN proton antiproton collider

With a segmented total absorption calorimeter of large acceptance, we have measured the total transverse energy spectrum for pp̄ collisions at s 1 2 = 540 GeV up to ΣE T= 130 GeV in the pseudo-rapidity range | η|< 1.5. Using two different algorithms, we have looked for localized depositions of transverse energy (jets). For ΣE T > 40 GeV, the fraction of events with two jets increases with ΣE T; this event structure is dominant for ΣE T > 100 GeV. We measure the inclusive jet cross section up to E T(jet) = 60 GeV and the two-jets mass distribution to 120 GeV/ c 2. The measured cross sections are compatible with the predictions of hard scattering models based on QCD.

Gluon bremsstrahlung effects in hadron-hadron collisions

We show that the inclusion of noncollinear gluon bremsstrahlung is essential in a quantum-chromodynamic (QCD) description of large transverse energy events in hadron-hadron collisions. Recent data from CERN and Fermilab for both large and small aperture energy triggers give indirect experimental support for QCD and for gluon bremsstrahlung effects.