842 research outputs found

    Identifying a new particle with jet substructures

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    We investigate a potential of measuring properties of a heavy resonance X, exploiting jet substructure techniques. Motivated by heavy higgs boson searches, we focus on the decays of X into a pair of (massive) electroweak gauge bosons. More specifically, we consider a hadronic Z boson, which makes it possible to determine properties of X at an earlier stage. For mXm_X of O(1) TeV, two quarks from a Z boson would be captured as a "merged jet" in a significant fraction of events. The use of the merged jet enables us to consider a Z-induced jet as a reconstructed object without any combinatorial ambiguity. We apply a conventional jet substructure method to extract four-momenta of subjets from a merged jet. We find that jet substructure procedures may enhance features in some kinematic observables formed with subjets. Subjet momenta are fed into the matrix element associated with a given hypothesis on the nature of X, which is further processed to construct a matrix element method (MEM)-based observable. For both moderately and highly boosted Z bosons, we demonstrate that the MEM with current jet substructure techniques can be a very powerful discriminator in identifying the physics nature of X. We also discuss effects from choosing different jet sizes for merged jets and jet-grooming parameters upon the MEM analyses.Comment: 36 pages, 11 figures, published in JHE

    The 750 GeV Diphoton Excess May Not Imply a 750 GeV Resonance

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    We discuss non-standard interpretations of the 750 GeV diphoton excess recently reported by the ATLAS and CMS Collaborations which do not involve a new, relatively broad, resonance with a mass near 750 GeV. Instead, we consider the sequential cascade decay of a much heavier, possibly quite narrow, resonance into two photons along with one or more invisible particles. The resulting diphoton invariant mass signal is generically rather broad, as suggested by the data. We examine three specific event topologies - the antler, the sandwich, and the 2-step cascade decay, and show that they all can provide a good fit to the observed published data. In each case, we delineate the preferred mass parameter space selected by the best fit. In spite of the presence of invisible particles in the final state, the measured missing transverse energy is moderate, due to its anti- correlation with the diphoton invariant mass. We comment on the future prospects of discriminating with higher statistics between our scenarios, as well as from more conventional interpretations.Comment: Discussion about the ATLAS Moriond EW2016 added. Matched to PRL accepted versio

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    OPTIMASS: A Package for the Minimization of Kinematic Mass Functions with Constraints

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    Reconstructed mass variables, such as M2M_2, M2CM_{2C}, MTM_T^\star, and MT2WM_{T2}^W, play an essential role in searches for new physics at hadron colliders. The calculation of these variables generally involves constrained minimization in a large parameter space, which is numerically challenging. We provide a C++ code, OPTIMASS, which interfaces with the MINUIT library to perform this constrained minimization using the Augmented Lagrangian Method. The code can be applied to arbitrarily general event topologies and thus allows the user to significantly extend the existing set of kinematic variables. We describe this code and its physics motivation, and demonstrate its use in the analysis of the fully leptonic decay of pair-produced top quarks using the M2M_2 variables.Comment: 39 pages, 12 figures, (1) minor revision in section 3, (2) figure added in section 4.3, (3) reference added and (4) matched with published versio

    Insulin Secretion and Incretin Hormone Concentration in Women with Previous Gestational Diabetes Mellitus

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    BackgroundWe examined the change in the levels of incretin hormone and effects of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) on insulin secretion in women with previous gestational diabetes (pGDM).MethodsA 75-g oral glucose tolerance test (OGTT) was conducted on 34 women with pGDM. In addition, 11 women with normal glucose tolerance, matched for age, height and weight, were also tested. The insulin, GIP, GLP-1, and glucagon concentrations were measured, and their anthropometric and biochemical markers were also measured.ResultsAmong 34 women with pGDM, 18 had normal glucose tolerance, 13 had impaired glucose tolerance (IGT) and 1 had diabetes. No significant differences were found in GLP-1 concentration between the pGDM and control group. However, a significantly high level of glucagon was present in the pGDM group at 30 minutes into the OGTT. The GIP concentration was elevated at 30 minutes and 60 minutes in the pGDM group. With the exception of the 30-minute timepoint, women with IGT had significantly high blood glucose from 0 to 120 minutes. However, there was no significant difference in insulin or GLP-1 concentration. The GIP level was significantly high from 0 to 90 minutes in patients diagnosed with IGT.ConclusionGLP-1 secretion does not differ between pGDM patients and normal women. GIP was elevated, but that does not seem to induce in increase in insulin secretion. Therefore, we conclude that other factors such as heredity and environment play important roles in the development of type 2 diabetes

    A Surgically Treated Case of Chronic Necrotizing Aspergillosis with Pleural Invasion

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    Aspergillus is a ubiquitous fungus and can cause many levels of disease severity. Chronic necrotizing aspergillosis is a rare disease and few cases have been reported in Korea. We experienced a case of pleural aspergillosis that was treated successfully with medical and surgical interventions. The 52-year-old man who was diagnosed with chronic necrotizing pulmonary aspergillosis underwent surgical treatment including a lobectomy, decortication, and myoplasty. The patient was also medically treated with amphotericin B followed by voriconazole. Pleural irrigation with amphotericin B was also performed. A multi-dimensional approach should be considered for treating chronic necrotizing pulmonary aspergillosis

    Reverberation Mapping of PG 0934+013 with the Southern African Large Telescope

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    We present the variability and time lag measurements of PG 0934+013 based on a photometric and spectroscopic monitoring campaign over a two year period. We obtained 46 epochs of data from the spectroscopic campaign, which was carried out using the Southern African Large Telescope with \sim1 week cadence over two sets of 4 month-long observing period, while we obtained 80 epochs of \textit{B}-band imaging data using a few 1-m class telescopes. Due to the seven month gap between the two observing periods, we separately measured the time lags of broad emission lines including Hβ\beta, by comparing the emission line light curve with the \textit{B}-band continuum light curve using the cross-correlation function techniques. We determined the Hβ\beta lag, τcent=8.462.14+2.08\tau_{\rm cent} = 8.46^{+2.08}_{-2.14} days in the observed-frame based on Year 2 data, while the time lag from Year 1 data was not reliably determined. Using the rms spectrum of Year 2 data, we measured the \Hb\ line dispersion \sigmaline = 668 ±\pm 44 \kms\ after correcting for the spectral resolution. Adopting a virial factor f = 4.47 from Woo et al. 2015, we determined the black hole mass MBH_{BH} = 3.130.93+0.91×1063.13 ^{+0.91} _{-0.93} \times 10^{6} \msun based on the \Hb\ time lag and velocity.Comment: 13 pages, 10 figures, ApJ in pres

    Pseudotumor of the Omentum Associated with Migration of the Ingested Crab-Leg

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    Foreign body ingestion is not uncommon in clinical practice, and it may occasionally lead to penetration injuries. Emergency physicians and radiologists sometimes fail to obtain complete histories including ingestion and may overlook the possibility of foreign body-induced complications. Herein, we report a case of stomach antrum perforation due to foreign body migration. We were unaware of the patient's history of eating the Korean delicacy "Kanjang-gaejang," which is raw crab seasoned with soy sauce. Several imaging diagnostic modalities had suggested the possibility of a malignant mass in the gastrocolic ligament area. During the operation, a crab leg was discovered as the cause of an intra-abdominal abscess. The patient underwent an antrectomy, a vagotomay, and a transverse colon wedge resection. We present this unusual case of a pseudotumorous lesion caused by ingestion of Kanjang-gaejang
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