The ALICE collaboration at the LHC reports measurement of the inclusive production cross section of electrons from semi-leptonic decays of beauty hadrons with rapidity $|y|<0.8$ and transverse momentum $1<p_{\mathrm{T}}<10$ GeV/$c$, in pp collisions at $\sqrt{s} = $ 2.76 TeV. Electrons not originating from semi-electronic decay of beauty hadrons are suppressed using the impact parameter of the corresponding tracks. The production cross section of beauty decay electrons is compared to the result obtained with an alternative method which uses the distribution of the azimuthal angle between heavy-flavour decay electrons and charged hadrons. Perturbative QCD calculations agree with the measured cross section within the experimental and theoretical uncertainties. The integrated visible cross section, $\sigma_{\mathrm{b} \rightarrow \mathrm{e}} = 3.47\pm0.40(\mathrm{stat})^{+1.12}_{-1.33}(\mathrm{sys})\pm0.07(\mathrm{norm}) \mu$b, was extrapolated to full phase space using Fixed Order plus Next-to-Leading Log (FONLL) predictions to obtain the total b$\bar{\mathrm{b}}$ production cross section, $\sigma_{\mathrm{b\bar{b}}} = 130\pm15.1(\mathrm{stat})^{+42.1}_{-49.8}(\mathrm{sys})^{+3.4}_{-3.1}(\mathrm{extr})\pm2.5(\mathrm{norm})\pm4.4(\mathrm{BR}) \mu$b.
Azimuthal correlation distribution between heavy-flavour decay electrons and charged hadrons, scaled by the number of electrons in minimum bias triggered events in the electron transverse momentum range 1.5-2.5 GeV/$c$.
Azimuthal correlation distribution between heavy-flavour decay electrons and charged hadrons, scaled by the number of electrons in minimum bias triggered events in the electron transverse momentum range 1.5-2.5 GeV/c.
Azimuthal correlation distribution between heavy-flavour decay electrons and charged hadrons, scaled by the number of electrons in EMCal triggered events in the electron transverse momentum range 4.5-6 GeV/$c$.
We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.
CP-folded electron charge asymmetry for data with $E_T^{e} > 25$ GeV multiplied by 100. $\langle|\eta^e|\rangle$ is the cross section weighted average of electron pseudorapidity in each bin from RESBOS with PHOTOS.
CP-folded electron charge asymmetry for data with $25 < E_T^{e} < 35$ GeV multiplied by 100. $\langle|\eta^e|\rangle$ is the cross section weighted average of electron pseudorapidity in each bin from RESBOS with PHOTOS.
CP-folded electron charge asymmetry for data with $E_T^{e} > 35$ GeV multiplied by 100. $\langle|\eta^e|\rangle$ is the cross section weighted average of electron pseudorapidity in each bin from RESBOS with PHOTOS.
The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5<y<4 and have been obtained by measuring the electron and muon pair decay channels, respectively. The integrated luminosities for the two channels are L^e_int=1.1 nb^-1 and L^mu_int=19.9 nb^-1, and the corresponding signal statistics are N_J/psi^e+e-=59 +/- 14 and N_J/psi^mu+mu-=1364 +/- 53. We present dsigma_J/psi/dy for the two rapidity regions under study and, for the forward-y range, d^2sigma_J/psi/dydp_t in the transverse momentum domain 0<p_t<8 GeV/c. The results are compared with previously published results at sqrt(s)=7 TeV and with theoretical calculations.
Double differential J/$\psi$ production cross section at $\sqrt{s}=2.76$ TeV. The first uncertainty is statistical, the second one is $p_{\rm T}$-coorelated, the third one is uncorrelated. Polarization-related uncertainties are not included.
The $\sqrt{s}$-dependence of $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ production (forward rapidity).
the $\sqrt{s}$-dependence of $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ production (forward rapidity).
The production of electrons from heavy-flavour hadron decays was measured as a function of transverse momentum ($p_{\rm T}$) in minimum-bias p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV with ALICE at the LHC. The measurement covers the $p_{\rm T}$ interval $0.5<p_{\rm T}<12$ GeV/$c$ and the rapidity range $-1.06 < y_{\rm cms} < 0.14$ in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor $R_{\rm pPb}$ was calculated by comparing the $p_{\rm T}$-differential invariant cross section in p-Pb collisions to a pp reference at the same centre-of-mass energy, which was obtained by interpolating measurements at $\sqrt{s}= 2.76$ TeV and $\sqrt{s} =7$ TeV. The $R_{\rm pPb}$ is consistent with unity within uncertainties of about 25%, which become larger for $p_{\rm T}$ below 1 GeV/$c$. The measurement shows that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-$p_{\rm T}$ yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects.
Double-differential cross section for the production of electrons, i.e. (electron + positron)/2, from heavy-flavour hadron decays as a function of transverse momentum for minimum-bias p--Pb collisions in the rapidity interval $-1.065 < y_{\rm cms} < 0.135$. The systematic uncertainties do not include an additional normalization uncertainty of 3.7%.
Nuclear modification factor $R_{\text{pPb}}$ of electrons from heavy-flavour hadron decays as a function of transverse momentum for minimum-bias p--Pb collisions in the rapidity interval $-1.065 < y_{\rm cms} < 0.135$.
We have studied the transverse-momentum ($p_{\rm T}$) dependence of the inclusive J/$\psi$ production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, in three center-of-mass rapidity ($y_{\rm cms}$) regions, down to zero $p_{\rm T}$. Results in the forward and backward rapidity ranges ($2.03 < y_{\rm cms} < 3.53$ and $-4.46 <y_{\rm cms}< -2.96$) are obtained by studying the J/$\psi$ decay to $\mu^+\mu^-$, while the mid-rapidity region ($-1.37 < y_{\rm cms} < 0.43$) is investigated by measuring the ${\rm e}^+{\rm e}^-$ decay channel. The $p_{\rm T}$ dependence of the J/$\psi$ production cross section and nuclear modification factor are presented for each of the rapidity intervals, as well as the J/$\psi$ mean $p_{\rm T}$ values. Forward and mid-rapidity results show a suppression of the J/$\psi$ yield, with respect to pp collisions, which decreases with increasing $p_{\rm T}$. At backward rapidity no significant J/$\psi$ suppression is observed. Theoretical models including a combination of cold nuclear matter effects such as shadowing and partonic energy loss, are in fair agreement with the data, except at forward rapidity and low transverse momentum. The implications of the p-Pb results for the evaluation of cold nuclear matter effects on J/$\psi$ production in Pb-Pb collisions are also discussed.
$p_{\rm T}$-differential inclusive cross section ${\rm d}^2\sigma^{J/\psi}/{\rm d}y{\rm d}p_{T}$ in the backward rapidity range (-4.46<$y_{\rm cms}$<-2.96). The first uncertainty is statistical, the second one is the $p_{\rm T}$-uncorrelated systematic uncertainty, while the third is the $p_{\rm T}$-correlated one.
$p_{\rm T}$-differential inclusive cross section ${\rm d}^2\sigma^{J/\psi}/{\rm d}y{\rm d}p_{T}$ in the mid-rapidity range (-1.37<$y_{\rm cms}$<0.43). The first uncertainty is statistical, the second one is the $p_{\rm T}$-uncorrelated systematic uncertainty, while the third is the $p_{\rm T}$-correlated one.
$p_{\rm T}$-differential inclusive cross section ${\rm d}^2\sigma^{J/\psi}/{\rm d}y{\rm d}p_{T}$ in the forward rapidity range (2.03<$y_{\rm cms}$<3.53). The first uncertainty is statistical, the second one is the $p_{\rm T}$-uncorrelated systematic uncertainty, while the third is the $p_{\rm T}$-correlated one.
We present a measurement of inclusive J/$\psi$ production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, $p_{\rm T}$, in the backward ($-4.46 < y_{\rm cms} < -2.96$) and forward ($2.03 < y_{\rm cms} < 3.53$) rapidity intervals in the dimuon decay channel and in the mid-rapidity region ($-1.37 < y_{\rm cms} < 0.43$) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The $p_{\rm T}$-differential J/$\psi$ production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average $p_{\rm T}$ and $p^2_{\rm T}$ values. The nuclear modification factor, $Q_{\rm pPb}$, is presented as a function of centrality for the three rapidity intervals, and, additionally, at backward and forward rapidity, as a function of $p_{\rm T}$ for several centrality classes. At mid- and forward rapidity, the J/$\psi$ yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. The degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing $p_{\rm T}$ of the J/$\psi$. At backward rapidity, the $Q_{\rm pPb}$ is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions.
Differential cross sections dsigma_JPsi/dydpt as function of pt at backward (-4.46<y_cms<-2.96) centre-of-mass rapidity. The first uncertainty is statistical, the second and third ones are the systematic uncertainties. The third uncertainty is fully correlated over pT.
Differential cross sections d^2sigma^cent_JPsi/dydpt as function of pt for six centrality classes at forward (2.03<y_cms<3.53) centre-of-mass rapidity. The first uncertainty is statistical, the second and third ones are the systematic uncertainties. The third uncertainty is fully correlated over pT.
Differential cross sections dsigma^cent_JPsi/dy for four centrality classes at mid-rapidity (-1.37<y_cms<0.43). The first uncertainty is statistical, the second and third ones are the systematic uncertainties. The third uncertainty is fully correlated over centrality.
We report on a CDF measurement of the total cross section and rapidity distribution, $d\sigma/dy$, for $q\bar{q}\to \gamma^{*}/Z\to e^{+}e^{-}$ events in the $Z$ boson mass region ($66<M_{ee}<116$GeV/c$^2$) produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$TeV with 2.1fb$^{-1}$ of integrated luminosity. The measured cross section of $257\pm16$pb and $d\sigma/dy$ distribution are compared with Next-to-Leading-Order(NLO) and Next-to-Next-to-Leading-Order(NNLO) QCD theory predictions with CTEQ and MRST/MSTW parton distribution functions (PDFs). There is good agreement between the experimental total cross section and $d\sigma/dy$ measurements with theoretical calculations with the most recent NNLO PDFs.
Total cross section integrated up to ABS(YRAP)=2.9.
Rapiditiy distribution of E+ E- pairs in the mass range from 66 to 116 GeV.
The transverse momentum ($p_{\rm T}$) dependence of the nuclear modification factor $R_{\rm AA}$ and the centrality dependence of the average transverse momentum $\langle p_{\rm T}\rangle$ for inclusive J/$\psi$ have been measured with ALICE for Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV in the e$^+$e$^-$ decay channel at mid-rapidity ($|y|<0.8$). The $\langle p_{\rm T}\rangle$ is significantly smaller than the one observed for pp collisions at the same centre-of-mass energy. Consistently, an increase of $R_{\rm AA}$ is observed towards low $p_{\rm T}$. These observations might be indicative of a sizable contribution of charm quark coalescence to the J/$\psi$ production. Additionally, the fraction of non-prompt J/$\psi$ from beauty hadron decays, $f_{\rm B}$, has been determined in the region $1.5 < p_{\rm T} < 10$ GeV/c in three centrality intervals. No significant centrality dependence of $f_{\rm B}$ is observed. Finally, the $R_{\rm AA}$ of non-prompt J/$\psi$ is discussed and compared with model predictions. The nuclear modification in the region $4.5 < p_{\rm T} < 10$ GeV/c is found to be stronger than predicted by most models.
The average transverse momentum $\langle p_{\rm T} \rangle$ of inclusive J/$\psi$ measured at mid-rapidity in centrality selected Pb-Pb collisions as a function of the number of participants.
The average transverse momentum squared $\langle p_{\rm T}^{2} \rangle$ of inclusive J/$\psi$ measured at mid-rapidity in centrality selected Pb-Pb collisions as a function of the number of participants.
The ratio $\langle p_{\rm T}^{2} \rangle_{\rm AA} / \langle p_{\rm T}^{2} \rangle_{\rm pp}$ of inclusive J/$\psi$ measured at mid-rapidity in centrality selected Pb-Pb collisions as a function of the number of participants.
The $p_{\rm T}$-differential production cross section of electrons from semileptonic decays of heavy-flavor hadrons has been measured at mid-rapidity in proton-proton collisions at $\sqrt{s} = 2.76$ TeV in the transverse momentum range 0.5 < $p_{\rm T}$ < 12 GeV/$c$ with the ALICE detector at the LHC. The analysis was performed using minimum bias events and events triggered by the electromagnetic calorimeter. Predictions from perturbative QCD calculations agree with the data within the theoretical and experimental uncertainties.
Double-differential cross section for the production of electrons, i.e. (electron + positron)/2, from heavy-flavour hadron decays as a function of transverse momentum at mid-rapidity. The systematic uncertainties do not include an additional normalization uncertainty of 1.9%.
The production of Z bosons is studied in the dimuon and dielectron decay channels in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV, using data collected by the CMS experiment at the LHC. The PbPb data sample corresponds to an integrated luminosity of about 150 inverse microbarns, while the pp data sample collected in 2013 at the same nucleon-nucleon centre-of-mass energy has an integrated luminosity of 5.4 inverse picobarns. The Z boson yield is measured as a function of rapidity, transverse momentum, and collision centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic nucleon-nucleon collisions, is found to be 1.06 +/- 0.05 (stat) +/- 0.08 (syst) in the dimuon channel and 1.02 +/- 0.08 (stat) +/- 0.15 (syst) in the dielectron channel, for centrality-integrated Z boson production. This binary collision scaling is seen to hold in the entire kinematic region studied, as expected for a colourless probe that is unaffected by the hot and dense QCD medium produced in heavy ion collisions.
The measured Z boson production cross section in pp collisions as a function of the Z boson pT for the dimuon decay channel in |y|<2.0.
The measured Z boson production cross section in pp collisions as a function of the Z boson pT for the dielectron decay channel in |y|<1.44.
The measured Z boson production cross section in pp collisions as a function of the Z boson rapidity for the dimuon decay channel.
The first search for single top quark production from the exchange of an $s$-channel virtual $W$ boson using events with an imbalance in the total transverse momentum, $b$-tagged jets, and no identified leptons is presented. The full data set collected by the Collider Detector at Fermilab, corresponding to an integrated luminosity of 9.45 fb$^{-1}$ from Fermilab Tevatron proton-antiproton collisions at a center of mass energy of 1.96 TeV, is used. Assuming the electroweak production of top quarks of mass 172.5 GeV/$c^2$ in the $s$-channel, a cross section of $1.12_{-0.57}^{+0.61}$ (stat+syst) pb, with a significance of 1.9 standard deviations, is measured. This measurement is combined with a previous result obtained from events with an imbalance in total transverse momentum, $b$-tagged jets, and exactly one identified lepton, yielding a cross section of $1.36_{-0.32}^{+0.37}$ (stat+syst) pb, with a significance of 4.2 standard deviations.
The s-channel single top quark cross section measured assuming top quarks of mass 172.5 GeV. The measurement uses a sample of events with large missing transverse energy, two or three jets of which one or more are b-tagged and no detected electron or muon candidates.
The combined s-channel single top quark cross section measurement assuming top quarks of mass 172.5 GeV. The measurement uses two samples of events. The first sample includes events with large missing transverse energy, two or three jets of which one or more are b-tagged and no detected electron or muon candidates. The second sample includes events with large missing transverse energy, one isolated muon or electron and two jets, at least one of which is b-tagged.
We present measurements of the forward-backward asymmetry in the angular distribution of leptons from decays of top quarks and antiquarks produced in proton-antiproton collisions. We consider the final state containing a lepton and at least three jets. The entire sample of data collected by the D0 experiment during Run II of the Fermilab Tevatron Collider, corresponding to 9.7 inverse fb of integrated luminosity, is used. The asymmetry measured for reconstructed leptons is $A_{FB}^l = \big(2.9 \pm 2.1(stat.) ^{+1.5}_{-1.7}(syst.) \big)$%. When corrected for efficiency and resolution effects within the lepton rapidity coverage of $|y_l|<1.5$, the asymmetry is found to be $A_{FB}^l = \big(4.2 \pm 2.3(stat.) ^{+1.7}_{-2.0}(syst.) \big)$%. Combination with the asymmetry measured in the dilepton final state yields $A_{FB}^l = \big(4.2 \pm 2.0(stat.) \pm 1.4(syst.) \big)$%. We examine the dependence of $A_{FB}^l$ on the transverse momentum and rapidity of the lepton. The results are in agreement with predictions from the next-to-leading-order QCD generator \mcatnlo, which predicts an asymmetry of $A_{FB}^l = 2.0$% for $|y_l|<1.5$.
Observed ASYMFB(LEPTON) as a function of PT(LEPTON) at reconstruction level.
Observed production-level ASYMFB(LEPTON) as a function of PT(LEPTON).
Observed production-level ASYMFB(LEPTON) as a function of ABS(YRAP(LEPTON)).
Using 7.3 pb-1 of ppbar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable \phistar, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the \phistar distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.
The measured PHI* distributions for the dielectron events corrected back to the particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.
The measured PHI* distributions for the dimuon events corrected back to the particle level. The distributions are normalised to unity inidividually for each abs(yrap) bin and channel.
We present a measurement of the forward-backward charge asymmetry ($A_{FB}$) in $p\bar{p} \to Z/\gamma^{*}+X \to e^+e^-+X$ events at a center-of-mass energy of 1.96 TeV using 1.1 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. $A_{FB}$ is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the $A_{FB}$ measurement to extract the effective weak mixing angle sin$^2\Theta^{eff}_W = 0.2327 \pm 0.0018 (stat.) \pm 0.0006 (syst.)$.
Unfolded forward-backward asymmetry as a function of the di-electron mass.
We present a measurement of the shape of the boson rapidity distribution for $p\bar{p}\to Z / \gamma^* \to e^+e^- + X$ events at a center-of-mass energy of 1.96 TeV. The measurement is made for events with electron-positron mass 71 < M_ee < 111 GeV and uses 0.4 $fb^{-1}$ of data collected at the Fermilab Tevatron collider with the D0 detector. This measurement significantly reduces the uncertainties on the rapidity distribution in the forward region compared with previous measurements. Predictions of NNLO QCD are found to agree well with the data over the full rapidity range.
Normalized rapidity distribution.
Details of systematic errors.
We report on measurements of inclusive cross sections times branching fractions into electrons for W and Z bosons produced in ppbar collisions at sqrts=1.8 TeV.From an integrated luminosity of 84.5 inverse pb recorded in 1994--1995 using the D0 detector at the Fermilab Tevatron, we determine sigma(ppbar->W+X)B(W->e nu) = 2310 +- 10(stat) +- 50(syst) +- 100(lum) pb and sigma(ppbar->Z+X)B(Z->e e) = 221 +- 3(stat) +- 4(syst) +- 10(lum) pb. From these, we derive their Ratio R = 10.43 +- 0.15(stat) +- 0.20(syst) +- 0.10(NLO), B(W->e nu) = 0.1066 +- 0.0015(stat) +- 0.0021(syst) +- 0.0011(theory)+- 0.0011(NLO), and Gamma_W = 2.130 +- 0.030(stat) +- 0.041(syst) +- 0.022(theory) +- 0.021(NLO) GeV. We use the latter to set a 95% confidence level upper limit on the partial decay width of the W boson into non-standard model final states, Gamma_W^{inv}, of 0.168 GeV. Combining these results with those from the 1992--1993 data gives R = 10.54 +- 0.24, Gamma_W = 2.107 +- 0.054 GeV, and a 95% C.L. upper limit on Gamma_W^{inv} of 0.132 GeV. Using a sample with a luminosity of 505 inverse nb taken at sqrts=630 GeV, we measure sigma(ppbar->W+X)B(W->e nu) = 658 +- 67 pb.
Cross sections times branching ratios for W+- and Z0 production. The second DSYS error is due to the uncertainty in the luminosity.
Ratio of W to Z0 cross sections. The second systematic error is due to the uncertainty in the NLO electroweak radiative corrections.
We present a measurement of the differential cross section as a function of transverse momentum of the Z boson in ppbar collisions at sqrt{s}=1.8 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider during 1994--1996. We find good agreement between our data and the NNLO resummation prediction and extract values of the non-perturbative parameters for the resummed prediction from a fit to the differential cross section.
Differential cross section in the electron channel. The errors contain both statistical and systematic error excluding the overall normalization error.
We present a measurement of the Drell-Yan cross section at high dielectron invariant mass using 120/pb of data collected in pbar-p collisions at sqrt(s) = 1.8 TeV by the D0 collaboration during 1992-96. No deviation from standard model expectations is observed. We use the data to set limits on the energy scale of quark-electron compositeness with common constituents. The 95% confidence level lower limits on the compositeness scale vary between 3.3 TeV and 6.1 TeV depending on the assumed form of the effective contact interaction.
Dielectron production cross section.
DO has measured the inclusive production cross section of W and Z bosons in a sample of 13 pb$^{-1}$ of data collected at the Fermilab Tevatron. The cross sections, multiplied by their leptonic branching fractions, for production in pbar-p collisions at sqrt{s}=1.8 TeV are sigma_W*B(W->e nu) = 2.36+-0.02+-0.08+-0.13 nb, sigma_W*B(W->mu nu) = 2.09+-0.06+-0.22+-0.11 nb, sigma_Z*B(Z->e+ e-) = 0.218+-0.008+-0.008+-0.012 nb, and sigma_Z*B(Z->mu+ mu-) = 0.178+-0.022+-0.021+-0.009 nb, where the first uncertainty is statistical and the second systematic; the third reflects the uncertainty in the integrated luminosity. For the combined electron and muon analyses, we find sigma_W*B(W->l mu)/sigma_Z*B(Z->l+ l-) = 10.90+-0.52. Assuming standard model couplings, we use this result to determine the width of the W boson, and obtain Gamma(W) = 2.044+-0.097 GeV.
No description provided.
Combined electron and muon analysis.
The gauge boson pair production processes Wg, WW, WZ, and Zg were studied using pbarp collisions corresponding to an integrated luminosity of ~14 pb-1 at a center-of-mass energy of sqrt(s) = 1.8 TeV. Analysis of Wg prod with subsequent W boson decay to lv (l=e,mu) is reported, including a fit to the pT spectrum of the photons which leads to limits on anomalous WWg couplings. A search for WW prod with subsequent decay to l-lbar-v-vbar (l=e,mu) is presented leading to an upper limit on the WW prod cross section and limits on anomalous WWg and WWZ couplings. A search for high pT W bosons in WW and WZ prod is described, where one W boson decays to an ev and the second W boson or the Z boson decays to two jets. A maximum likelihood fit to the pT spectrum of W bosons resulted in limits on anomalous WWg and WWZ couplings. A combined fit to the three data sets which provided the tightest limits on anomalous WWg and WWZ couplings is also described. Limits on anomalous ZZg and Zgg couplings are presented from an analysis of the photon ET spectrum in Zg events in the decay channels (ee, mu-mu, and v-vbar) of the Z boson.
CONST(NAME=SCALE) is the model parameter, used in the modification of the couplings as follows: h = hi0/(1 + M(gamma Z)**2/CONT(NAME=SCALE)**2)**n. See article for details.
We have measured the ZZ-gamma and Z-gamma-gamma couplings by studying p-bar p -> (missing ET) gamma + X events at sqrt(s)=1.8 TeV with the D0 detector at the Fermilab Tevatron Collider. This first study of hadronic Z-gamma production in the neutrino decay channel gives the most stringent limits on anomalous couplings available. A fit to the transverse energy spectrum of the photon in the candidate event sample, based on a data set corresponding to an integrated luminosity of 13.1 pb~(-1), yields 95% CL limits on the anomalous CP-conserving ZZ-gamma couplings of |h~Z_(30)|<0.9, |h~Z_(40)|<0.21, for a form-factor scale Lambda = 500 GeV. Combining these results with our previous measurement using Z -> ee and mu-mu yields the limits:|h~Z_(30)|<0.8, |h~Z_(40)|<0.19 (Lambda = 500 GeV) and |h~Z_(30)|<0.4, |h~Z_(40)|<0.06 (Lambda = 750 GeV).
CONST(NAME=SCALE) is the model parameter, used in the modification of the couplings as follows: h = hi0/(1 + M(gamma Z)**2/CONT(NAME=SCALE)**2)**n. See article for details.. The data with Z --> lepton+ lepton- is taken from S.Abachi, PRL 75, 1028.
A search for a heavy charged gauge boson, W ′, using the decay channels W ′ → eν and W′ → τν → eνν ν is reported. The data used in the analysis were collected by the DØ experiment at the Fermilab Tevatron during the 1992-93 p p collider run from an integrated luminosity of 13.9 ± 0.8 pb −1 at s =1.8 TeV . Assuming that the neutrino from W ′ decay is stable and has a mass significantly less than m W ′ , an upper limit at the 95% confidence level is set on the cross section times branching ratio for p p → W′ → eν . A W ′ with the same couplings to quarks and leptons as the standard model W boson is excluded for m W ′ < 610 GeV/c 2 .
No description provided.
The W'+- is assumed has the couplings to quarks and leptons as the standard model W and neutrinos produced in WPRIME decay are stable and have a mass significantly less then M(W').
The inclusive cross sections times leptonic branching ratios for W and Z boson production in PbarP collisions at Sqrt(s)=1.8 TeV were measured using the D0 detector at the Fermilab Tevatron collider: Sigma_W*B(W->e, nu) = 2.36 +/- 0.07 +/- 0.13 nb, Sigma_W*B(W->mu,nu) = 2.09 +/- 0.23 +/- 0.11 nb, Sigma_Z*B(Z-> e, e) = 0.218 +/- 0.011 +/- 0.012 nb, Sigma_Z*B(Z->mu,mu) = 0.178 +/- 0.030 +/- 0.009 nb. The first error is the combined statistical and systematic uncertainty, and the second reflects the uncertainty in the luminosity. For the combined electron and muon analyses we find: [Sigma_W*B(W->l,nu)]/[Sigma_Z*B(Z->l,l)] = 10.90 +/- 0.49. Assuming Standard Model couplings, this result is used to determine the width of the W boson: Gamma(W) = 2.044 +/- 0.093 GeV.
The second DSYS error is due to luminosity.
Forum