Jacobian Peak Research Articles

Determination of the W-boson mass at hadron colliders

We introduce an observable relevant for the determination of the W-boson mass mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} at hadron colliders. This observable is defined as an asymmetry around the jacobian peak of the charged-lepton transverse-momentum distribution in the charged-current Drell–Yan process. We discuss the observable’s theoretical prediction, presenting results at different orders in QCD, and showing its perturbative stability. Its definition as a single scalar number and its linear sensitivity to mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} allow a clean extraction of the latter and a straightforward discussion of the associated theoretical systematics: a perturbative QCD uncertainty of O(±5)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{{\\mathcal {O}}}}(\\pm 5)$$\\end{document} MeV on mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} can be established by means of this observable, relying solely on charged-current Drell–Yan information. Owing to its relatively inclusive nature, the observable displays desirable properties also from the experimental viewpoint, especially for the unfolding of detector effects. We show that a measurement of this observable can lead to a competitive experimental error on mW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$m_W$$\\end{document} at the LHC.

Nitrous Oxide Profile Retrievals from Atmospheric Infrared Sounder and Validation

This paper presents an algorithm for the retrieval of nitrous oxide profiles from the Atmospheric InfraRed Sounder (AIRS) on the Earth Observing System (EOS)/Aqua using a nonlinear optimal estimation method. First, an improved Optimal Sensitivity Profile (OSP) algorithm for channel selection is proposed based on the weighting functions and the transmissions of the target gas and interfering gases, with 13 channels selected for inversion in this algorithm. Next, the data of the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations (HIPPO) aircraft and the Earth System Research Laboratory (ESRL) are used to verify the retrieval results, including the atmospheric nitrous oxide profile and the column concentration. The results show that using AIRS satellite data, the atmospheric nitrous oxide profile between 300–900 hPa can be well retrieved with an accuracy of ~0.1%, which agrees with the corresponding Jacobian peak interval of selected channels. Analysis of the AIRS retrievals demonstrates that the AIRS measurements provide useful information to capture the spatial and temporal variations in nitrous oxide between 300–900 hPa.

Drell-Yan qT resummation of fiducial power corrections at N3LL

We consider Drell-Yan production pp → V*X → LX at small qT ≪ Q, where qT and Q are the total transverse momentum and invariant mass of the leptonic final state L. Experimental measurements require fiducial cuts on L, which in general introduce enhanced, linear power corrections in qT/Q. We show that they can be unambiguously predicted from factorization, and resummed to the same order as the leading-power contribution. For the fiducial qT spectrum, they constitute the complete linear power corrections. We thus obtain predictions for the fiducial qT spectrum to N3LL and next-to-leading-power in qT/Q. Matching to full NNLO ( {alpha}_s^2 ), we find that the linear power corrections are indeed the dominant ones, and once included by factorization, the remaining fixed-order corrections become almost negligible below qT ≲ 40 GeV. We also discuss the implications for more complicated observables, and provide predictions for the fiducial ϕ* spectrum at N3LL+NNLO. We find excellent agreement with ATLAS and CMS measurements of qT and ϕ*. We also consider the {p}_T^{mathrm{ell}} spectrum. We show that it develops leptonic power corrections in qT/(Q − 2 {p}_T^{mathrm{ell}} ), which diverge near the Jacobian peak {p}_T^{mathrm{ell}} ∼ Q/2 and must be kept to all powers to obtain a meaningful result there. Doing so, we obtain for the first time an analytically resummed result for the {p}_T^{mathrm{ell}} spectrum around the Jacobian peak at N3LL+NNLO. Our method is based on performing a complete tensor decomposition for hadronic and leptonic tensors. We show that in practice this is equivalent to often-used recoil prescriptions, for which our results now provide rigorous, formal justification. Our tensor decomposition yields nine Lorentz-scalar hadronic structure functions, which for Z/γ* → ℓℓ or W → ℓν directly map onto the commonly used angular coefficients, but also holds for arbitrary leptonic final states. In particular, for suitably defined Born-projected leptons it still yields a LO-like angular decomposition even when including QED final-state radiation. Finally, we also discuss the application to qT subtractions. Including the unambiguously predicted fiducial power corrections significantly improves their performance, and in particular makes them applicable near kinematic edges where they otherwise break down due to large leptonic power corrections.

Proposal for chiral-boson search at LHC via their unique new signature

The resonance production of new chiral spin-1 bosons and their detection through the Drell-Yan process at the CERN LHC is considered. Quantitative evaluations of various differential cross sections of the chiral-boson production are made within the CalcHEP package. The new neutral chiral bosons can be observed as a Breit-Wigner resonance peak in the invariant-dilepton-mass distribution, as usual. However, unique new signatures of the chiral bosons exist. First, there is no Jacobian peak in the lepton transverse-momentum distribution. Second, the lepton angular distribution in the Collins—Soper frame for the high on-peak invariant masses of the lepton pairs has a peculiar “swallowtail” shape.

Inclusive Jet ET Distributions and Light Gluinos.

In the light gluino variant of the minimal supersymmetric model gluino pairs can be readily produced in collider experiments even if the squarks are arbitrarily heavy. This enhances the jet transverse energy distributions. In addition the slower running of the strong coupling constant in the presence of light gluinos leads to a further enhancement at higher transverse energies relative to the standard $QCD$ expectations. Finally, the enhanced squark gluino production would lead to a Jacobian peak in the $E_T$ distribution at about $M_{\tilde Q}/2$. These effects are of about the right magnitude to explain anomalies observed by the $CDF$ and $D0$ collaborations.

Chargino-neutralino production in $$p\bar p$$ -collisions for the left-right supersymmetric model

An extension of the supersymmetric standard model to the supersymmetric SU(2)$\sb{\rm L}$ x SU(2)$\sb{\rm R}$ x U(1)$\sb{\rm B-L}$ model is considered. The gauge group contains bi-doublet and triplet Higgs fields. In this work we have considered chargino (charged gauginos mixed with higgsinos) and neutralino (neutral gauginos mixed with higgsinos) eigenstates for the left-right supersymmetric (L-R SUSY) model. After mixing, in the minimal supersymmetric model (MSSM), there are two charginos and four neutralinos. In the L-R supersymmetric model, in addition to four charginos there are three neutralinos generated from the first symmetry breaking, and four neutralinos generates from the second symmetry breaking. The mixings are in general model dependent. In the minimal SUSY and L-R SUSY models, these mixings can be parameterized in terms of a few parameters. We find analytical expressions and numerical solutions for the mass eigenstates with some restrictions on the L-R parameters. We also investigate the possibility of detecting chargino and neutralino production in pp-collisions at CDF, namely $\rm p\bar{p}\to W\sbsp{L,R}{-} + X\to\ \sbsp{\chi\sb{j}}{\sim\sb-}\sbsp{\chi\sb{i}}{\sim0} + X.$ The expressions for these inclusive cross-sections are solved numerically, using parton model distributions. We have used $\rm \tilde{M}\sb\chi -= 45\ GeV,$ tan$\beta$ = 1 and a lower bound on the lightest supersymmetric particle (LSP) mass, $\tilde\chi$ = 14 GeV. Finally we take $\rm M\sb{WR}\ge 300$ GeV for $\rm g\simeq g\sb{L}\simeq g\sb{R}.$ In the pp-center of mass frame we find the cross sections are: $\rm \sigma\sb{L}(p\bar{p}\to W\sbsp{L}{-} + X\to\sbsp{\chi\sb{j}}{\sim\sb-}\sbsp{\chi\sb{i}}{\sim0} + X)\approx0.11$ nb, and $\rm \sigma\sb{R}(p\bar{p}\to W\sbsp{R}{-} + X\to\sbsp{\chi\sb{j}}{\sim\sb-}\sbsp{\chi\sb{i}}{\sim0} + X)\approx4.6$ pb, and thus $\rm \sigma\sb{L}\ge24\sigma\sb{R}$ at $\sqrt{\rm s}$ = 1.8 TeV. Cross sections are also given for larger values of the center of mass energy $\sqrt{\rm s}$ up to those available at the SSC. The results are compared with the prompt-lepton background of the $\rm W\sbsp{L,R}{-}$ decays from $\rm p\bar{p}\to W\sbsp{L,R}{-} + X\to\ell\sp-\nu\sb{\ell L,R} + X.$ Both decays for $\rm W\sbsp{L,R}{-}$-bosons show Jacobian peaks for $\rm p\sb{T} = \sqrt{\{s}}/2\simeq M\sb{WL}/2\simeq40$ GeV $\rm (p\sb{T}\simeq 150$ GeV for M$\sb{\rm WR})$ at $\theta=90\sp\circ.$ Furthermore the chargino signature unlike the prompt-lepton background is symmetric under the Jacobian peak. We also exhibit the dependence of the angular distribution of the chargino on the c.m angle $\theta$ for $\rm p\sb{T} = 40$ GeV, 150 GeV at $\sqrt{\rm s} = 1.8$ TeV.

Top quark detection via W+ n jet measurements

In t t and W production at p p colliders, top quark semileptonic decays t→bℓ ν contribute to the same class of events as W→ℓ ν decays. The top contribution is particularly significant in n⩾2 jet events and can be observed (a) as a distortion in the ℓν transverse mass distribution below the W→ℓ ν jacobian peak if m t< M w; (b) as a systematic increase in the jet multiplicity distribution at large n for any m t; (c) as a shift in the apparent ( W+n jet) ( Z+n jet) event ratio at large n for any m t. The observation of a top quark signal in these ways does not require prior elimination of the W background.

Super Drell-Yan processes as genuine sources of winos and zinos

In supersymmetric QCD the squark contents of the nucleon allows the production in p p collisions of W̃ ± and Z̃ 0 via the subprocesses q ̃ ( q ̃ )+ q ( q)→ W ̃ ± or Z ̃ 0 . Like in the W case the transverse momentum distribution of the leptons issued from the decays W ̃ ±→ℓ ± v ̃ or Z ̃ →ℓ ± o ̃ l ∓ will present a jacobian peak. This should constitute a remarkable signature for these processes. We estimate total rates and present shapes of lepton spectra for a large range of W̃ ± and Z̃ 0 masses.

Testing supersymmetry interpretations of anomalous missing-pT events observed at the CERN pp-bar collider.

We compare predictions of three supersymmetry scenarios [(A) ${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$&gt;${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}50 GeV, (B) ${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$&gt;${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}50 GeV, and (C) ${m}_{q\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}100 GeV, ${m}_{g\ifmmode \tilde{}\else \~{}\fi{}}$ \ensuremath{\simeq}3 GeV] proposed to explain large-missing-${p}_{T}$ events at the CERN pp\ifmmode\bar\else\textasciimacron\fi{} collider in terms of scalar-quark or gluino decays to a light photino. We evaluate fusion cross sections for monojets and multijets and present distributions in missing ${p}_{T}$, jet ${E}_{T}$, jet pseudorapidity, jet invariant mass, and cluster transverse mass. Scenarios A and B give about equal one-jet and two-jet event rates, soft missing-${p}_{T}$ and jet-${E}_{T}$ distributions and occasional prompt leptons; scenario B gives large jet invariant masses, even for monojets. Scenario C yields monojet dominance and Jacobian peaks in missing ${p}_{T}$ and jet ${E}_{T}$; the present UA1 data favor this latter description.

Sharpening up the signal

Abstract We investigate distinguishing characteristics of lepton + jet events arising from W → t b production with t→blν decay at p p colliders. In two-jet events transverse masses have joint jacobian peaks just below and above m t associated with the t and b fragments and just below M W associated with the t b cluster. The lepton + one-jet events of W → t b origin also give distributions with striking features. Other useful diagnostics for t quark identification are presented, including those of t t hadroproduction

Non-leading QCD contributions in W boson production

We calculate the transverse momentum distribution of decay-leptons from W bosons produced in p p scattering. It is shown that the inclusion of non-leading QCD contributions induces a remarkable change on the shape of the jacobian peak. We propose the use of the complete QCD formula to make a meaningful analysis of the experimental data.

Possible Supersymmetry Scenario forpp―Collider Monojet Events and Unaccompanied "Photon" Events

Anomalous missing-${p}_{T}$ events observed at the CERN $p\stackrel{-}{p}$ collider can be plausibly explained by the photino decay mode $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}\ensuremath{\rightarrow}q\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\gamma}}$ of scalar quarks with mass \ensuremath{\sim} 100 GeV. This gives a Jacobian peak in the jet ${p}_{T}$ distribution suggested by the data of Arnison et al. Two-photon decays of ${\ensuremath{\pi}}^{0}$, $\ensuremath{\eta}$, ${\ensuremath{\eta}}^{\ensuremath{'}}$ may account for the "photon" events. To account for the reported rates and to avoid gluino mass limits, the gluino and photino must be light and nearly degenerate.

Transverse momentum distributions for weak bosons at the pp̄ collider

The effect of subleading corrections to multiple soft gluon emission is shown dramatically change the k ⊥ distributions of weak bosons predicted from leading resummed to all orders in α S. The resulting spectrum is found much narrower, reducing the expected broadning of the jacobian peak in the lepton momentum distribution.

Finding the t-quark in W boson decay debris

We point out a spectacular jet plus electron signature of t-quark production at p p colliders via W boson decay W→ t b with subsequent b→jet, and t → b eν decays. The b jet momentum transverse to the beam has a jacobian peak near p T ( b)= (M W 2−m t 2) 2M W ; this jet is expected to be highly collimated. Electrons from t -decay ocur with large momentum components normal to the b jet in the plane transverse to the beam. Both the b jacobian peak and transverse momenta of the t -decay fragments can be used in making further determinations of m t.

Transverse Mass and Width of theWBoson

The possibility that both the mass and the width of the W boson can be measured by the Jacobian peak in the transverse mass distribution is proposed and examined.

Method for W ± boson mass determination in p̄p collisions

Events where a hadronic jet is produced along with a W ± boson that decays leptonically may allow a cleaner W mass determination than the standard jacobian peak method. The lepton momentum distribution normal to the production plane (specified by the recoil jet) has the simple form 1− 4 3 ) p 2 N M 2 W with an end-point at p N = 1 2 M W that is not smeared by the W recoil against the jet. Furthermore, the event selection reduces heavy quark decay backgrounds. The electron contribution from W→ τν is also calculated.

Search for nucleon resonances of mass up to 8.5 GeV

Missing mass spectra were obtained by measuring recoil protons from the reaction p+p→p+X in the Jacobian peak region. Data were taken during the acceleration ramp of the Fermilab machine using an internal hydrogen gas jet target. We observe the well known N ∗(1688) and N ∗(2190) resonances but no significant structures at higher mass.

A high resolution, high statistics baryon spectrometer

A magnet-less spectrometer consisting of a point hydrogen target and a scintillation counter hodoscope is described. Recoil protons are selected on the basis of range, time-of-flight, and pulse height. The hodoscope measures the recoil angle in the region of the Jacobian peak. The incident proton momentum, which varies in each event, is measured at each trigger time. Data are displayed directly on a 2-dimensional pulse height analyser, one dimension being the recoil angle, the other the incident momentum, the combination of these giving the mass spectrum.

Evidence forη0andω0Meson Production in the Reactionp+d→He3+MissingMass

Strong ${\ensuremath{\pi}}^{0}$, ${\ensuremath{\eta}}^{0}$, and ${\ensuremath{\omega}}^{0}$ peaks have been observed in the reaction $p+d\ensuremath{\rightarrow}{\mathrm{He}}^{3}+\mathrm{missing}\mathrm{mass}$ at incident proton momenta of 3.5-3.8 GeV/c and proton-to-meson momentum transfer $t=\ensuremath{-}1.5$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The mesons are produced with center-of-mass cross sections on the order of ${10}^{\ensuremath{-}34}$ ${\mathrm{cm}}^{2}$/sr at a center-of-mass angle of about 60\ifmmode^\circ\else\textdegree\fi{}. The missing-mass spectrometer combined the Jacobian peak and the orthogonal dispersion techniques.

Observation of charged ρ-meson and its properties using a missing-mass spectrometer

Presented is the mass spectrum of charged bosons in the mass region (650÷850) MeV, obtained with a missing-mass spectrometer (MMS) operating on the principle of « Jacobian peaks in angular distribution » (1). The unstable bosons, x−, are produced in reaction π−+p → p+x− at incident momentap1=(3.0±0.1), (3.5±0.1), (4.5±0.045) and (5.05±0.05) GeV/c.