Measurements of the midrapidity transverse energy distribution, $d\Et/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $d\Et/d\eta$ distributions are first compared with the number of nucleon participants $N_{\rm part}$, number of binary collisions $N_{\rm coll}$, and number of constituent-quark participants $N_{qp}$ calculated from a Glauber model based on the nuclear geometry. For Au$+$Au, $\mean{d\Et/d\eta}/N_{\rm part}$ increases with $N_{\rm part}$, while $\mean{d\Et/d\eta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/d\eta \propto (1-x) N_{\rm part}/2 + x N_{\rm coll}$, which has been used to represent $E_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\rm coll}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_{T}/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Et EMC distributions for sqrt(sNN) = 62.4 GeV Au+Au collisions shown in 5% wide centrality bins.
Results are presented from a study of the structure of high energy hadronic events recorded by the L3 detector at sqrt(s)>192 GeV. The distributions of several event shape variables are compared to resummed O(alphaS^2) QCD calculations. We determine the strong coupling constant at three average centre-of-mass energies: 194.4, 200.2 and 206.2 GeV. These measurements, combined with previous L3 measurements at lower energies, demonstrate the running of alphaS as expected in QCD and yield alphaS(mZ) = 0.1227 +- 0.0012 +- 0.0058, where the first uncertainty is experimental and the second is theoretical.
The measured ALPHA_S at three centre-of-mass energies from fits to the individual event shape distributions. The first error is statistcal, the first DSYS error is the experimental systematic uncertainty, and the second DSYS error is the theoryuncertainty.
Updated ALPHA_S measurements from the BT, BW and C-Parameter distributions,from earlier L3 data at lower centre-of-mass energies.. The first error is the total experimental error (stat+sys in quadrature) and the DSYS error is the theory uncertainty.
Combined ALPHA_S values from the five event shape variables. The first error is statistical, the first DSYS error is the experimental systematic uncertainity, the second DSYS error is the uncertainty from the hadronisdation models, andthethird DSYS errpr is the uncertainty due to uncalculated higher orders in the QCDpredictions.
Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 189GeV using the OPAL detector at LEP. Results are presented for event topologies consistent with a single photon or with an acoplanar photon pair. Cross-section measurements are performed within the kinematic acceptance of each selection, and the number of light neutrino species is measured. Cross-section results are compared with the expectations from the Standard Model process e+e- to nu nubar + photon(s). No evidence is observed for new physics contributions to these final states. Upper limits are derived on sigma(e+e- to XY).BR(X to Y gamma) and sigma(e+e- to XX).BR**2(X to Y gamma) for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos (X=nu*, Y = nu), to neutralino production (X=neutralino_2, Y=neutralino_1) and to supersymmetric models in which X = neutralino_1 and Y = light gravitino. The case of macroscopic decay lengths of particle X is considered for e+e- to XX, X to Y gamma, when M_Y is of order zero. The single-photon results are also used to place upper limits on superlight gravitino pair production as well as graviton-photon production in the context of theories with additional space dimensions.
No description provided.
We have reconstructed the radiative decays $\chi_{b}(1P) \to \Upsilon(1S) \gamma $ and $\chi_{b}(2P) \to \Upsilon(1S) \gamma $ in $p \bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV, and measured the fraction of $\Upsilon(1S)$ mesons that originate from these decays. For $\Upsilon(1S)$ mesons with $p^{\Upsilon}_{T}>8.0$ GeV/$c$, the fractions that come from $\chi_{b}(1P)$ and $\chi_{b}(2P)$ decays are $(27.1\pm6.9(stat)\pm4.4(sys))%$ and $(10.5\pm4.4(stat)\pm1.4(sys))%$, respectively. We have derived the fraction of directly produced $\Upsilon(1S)$ mesons to be $(50.9\pm8.2(stat)\pm9.0(sys))%$.
No description provided.
We present a measurement of the forward-backward charge asymmetry of the process pp¯→Z0/γ+X,Z0/γ→e+e− at Mee>MZ, using 110pb−1 of data at s=1.8TeV collected at the Collider Detector at Fermilab. The measured charge asymmetries are 0.43±0.10 in the invariant mass region Mee>105GeV/c2, and 0.070±0.016 in the region 75<Mee<105GeV/c2. These results are consistent with the standard model values of 0.528±0.009 and 0.052±0.002, respectively.
The forward-backward asymmetry resuts from angular differential cross section : D(SIG)/D(COS(THETA*) = A*(1 + COS(THETA*)**2) + B*COS(THETA*), where THETA * is the emission angle of the E- relative to the quark momentum in the rest frame of the E+ E- pair.
Short overview of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E = 400 - 1400 MeV and preliminary results of data analysis are presented.
No description provided.
No description provided.
No description provided.
We present results for the charged-particle multiplicity distribution at mid-rapidity in Au - Au collisions at sqrt(s_NN)=130 GeV measured with the PHENIX detector at RHIC. For the 5% most central collisions we find $dN_{ch}/d\eta_{|\eta=0} = 622 \pm 1 (stat) \pm 41 (syst)$. The results, analyzed as a function of centrality, show a steady rise of the particle density per participating nucleon with centrality.
130 GeV is sqrt(S) per nucleon-nucleon collision. N(C=N_NUCLEONS) and N(C=N_COLLISONS) are the number of participating nucleons and binary collisions. The statistical errors are negligible and only systematic errors are quoted. COL(NAME=CENTRALITY) is centrality.
The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
PT RANGE FROM 0 TO INFINITY.
PT RANGE FROM 0 TO INFINITY.
No description provided.
The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity $|y_{ee}|<1$ in minimum-bias Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened $\rho$ spectral function for $M_{ee}<1.1$ GeV/$c^{2}$. The integrated dielectron excess yield at $\sqrt{s_{NN}}$ = 19.6 GeV for $0.4<M_{ee}<0.75$ GeV/$c^2$, normalized to the charged particle multiplicity at mid-rapidity, has a value similar to that in In+In collisions at $\sqrt{s_{NN}}$ = 17.3 GeV. For $\sqrt{s_{NN}}$ = 200 GeV, the normalized excess yield in central collisions is higher than that at $\sqrt{s_{NN}}$ = 17.3 GeV and increases from peripheral to central collisions. These measurements indicate that the lifetime of the hot, dense medium created in central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV is longer than those in peripheral collisions and at lower energies.
Reconstructed dielectron unlike-sign pairs, like-sign pairs and signal distributions, together with the signal to background ratio (S/B). All columns are presented as a function of dielectron invariant mass in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV.
Dielectron invariant mass spectrum in the STAR acceptance (|$y_{ee}$| < 1, 0.2 < $p_T^e$ < 3 GeV/c, |$\eta^e$ | < 1) after efficiency correction in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV.
Hadronic cocktail consisting of the decays of light hadrons and correlated decays of charm in Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 GeV.
A search for the quantum chromodynamics (QCD) critical point was performed by the STAR experiment at the Relativistic Heavy Ion Collider, using dynamical fluctuations of unlike particle pairs. Heavy-ion collisions were studied over a large range of collision energies with homogeneous acceptance and excellent particle identification, covering a significant range in the QCD phase diagram where a critical point may be located. Dynamical $K\pi$, $p\pi$, and $Kp$ fluctuations as measured by the STAR experiment in central 0-5\% Au+Au collisions from center-of-mass collision energies $\rm \sqrt{s_{NN}}$ = 7.7 to 200 GeV are presented. The observable $\rm \nu_{dyn}$ was used to quantify the magnitude of the dynamical fluctuations in event-by-event measurements of the $K\pi$, $p\pi$, and $Kp$ pairs. The energy dependences of these fluctuations from central 0-5\% Au+Au collisions all demonstrate a smooth evolution with collision energy.
$p\pi$, Kp, and $K\pi$ fluctuations as a function of collision energy, expressed as $v_{dyn,p\pi}$, $v_{dyn,Kp}$, and $v_{dyn,K\pi}$ respectively. Shown are data from central (0-5%) Au+Au collisions at energies from $\sqrt{s_{\rm NN}}$ = 7.7 to 200 GeV from the STAR experiment.
We present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au+Au collisions for energies ranging from $\sqrt{s_{NN}}=7.7$ GeV to 200 GeV. The third harmonic $v_3^2\{2\}=\langle \cos3(\phi_1-\phi_2)\rangle$, where $\phi_1-\phi_2$ is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs $\Delta\eta = \eta_1-\eta_2$. Non-zero {\vthree} is directly related to the previously observed large-$\Delta\eta$ narrow-$\Delta\phi$ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity Quark Gluon Plasma (QGP) phase. For sufficiently central collisions, $v_3^2\{2\}$ persist down to an energy of 7.7 GeV suggesting that QGP may be created even in these low energy collisions. In peripheral collisions at these low energies however, $v_3^2\{2\}$ is consistent with zero. When scaled by pseudorapidity density of charged particle multiplicity per participating nucleon pair, $v_3^2\{2\}$ for central collisions shows a minimum near {\snn}$=20$ GeV.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
Representative results on $v_3^2\{2\}$ from Au+Au collisions as a function of $\Delta\eta$ for charged hadrons with pT > 0.2 GeV/c and |$\eta$| < 1.
None
No description provided.
No description provided.
No description provided.
Flavour inclusive, udsc and b fragmentation functions in unbiased jets, and flavour inclusive, udsc, b and gluon fragmentation functions in biased jets are measured in e+e- annihilations from data collected at centre-of-mass energies of 91.2, and 183-209 GeV with the OPAL detector at LEP. The unbiased jets are defined by hemispheres of inclusive hadronic events, while the biased jet measurements are based on three-jet events selected with jet algorithms. Several methods are employed to extract the fragmentation functions over a wide range of scales. Possible biases are studied in the results are obtained. The fragmentation functions are compared to results from lower energy e+e- experiments and with earlier LEP measurements and are found to be consistent. Scaling violations are observed and are found to be stronger for the fragmentation functions of gluon jets than for those of quarks. The measured fragmentation functions are compared to three recent theoretical next-to-leading order calculations and to the predictions of three Monte Carlo event generators. While the Monte Carlo models are in good agreement with the data, the theoretical predictions fail to describe the full set of results, in particular the b and gluon jet measurements.
The udsc jet fragmentation function in bins of $x_{\rm E}$ and scale. The scale denotes $Q_{\rm jet}$ for the biased jets and is given by the intervals, while it denotes $\sqrt{s}/2$ for the unbiased jets and is given by the single values. These data are displayed in Fig.7.
The b jet fragmentation function in bins of $x_{\rm E}$ and scale. The scale denotes $Q_{\rm jet}$ for the biased jets and is given by the intervals, while it denotes $\sqrt{s}/2$ for the unbiased jets and is given by the single values. These data are displayed in Fig. 8. In the region 0.48 $<x_{\rm E}<$ 0.90 and $Q_{\rm jet}=$ 30-70 GeV, no measurement was possible due to low statistics.
The gluon jet fragmentation functions in bins of $x_{\rm E}$ and scale $Q_{\rm jet}$ obtained from the biased jets using the b-tag method (BT). These data are displayed in Fig. 9. In the region 0.48 $<x_{\rm E}<$ 0.90 and $Q_{\rm jet}=$ 30-42 GeV for the b-tag method, no measurement was possible due to low statistics.
We present results obtained from a study of the structure of hadronic events recorded by the L3 detector at various centre-of-mass energies. The distributions of event shape variables and the energy dependence of their mean values are measured from 30GeV to 189GeV and compared with various QCD models. The energy dependence of the moments of event shape variables is used to test a power law ansatz for the non-perturbative component. We obtain a universal value of the non-perturbative parameter alpha_0 = 0.537 +/- 0.073. From a comparison with resummed O(alpha_s^2) QCD calculations, we determine the strong coupling constant at each of the selected energies. The measurements demonstrate the running of alpha_s as expected in QCD with a value of alpha_s(m_Z) = 0.1215 +/- 0.0012 (exp) +/- 0.0061 (th).
Distribution for THRUST at c.m. energy 189 GeV.
Distribution for Heavy Jet Mass at c.m. energy 189 GeV.
Distribution for Total Jet Broadening at c.m. energy 189 GeV.
We present a measurement of the transverse momentum distribution of dielectron pairs with invariant mass near the mass of the Z boson. The data were obtained using the DO detector during the 1994-1995 run of the Tevatron Co!lider at Fermilab. The data used in the measurement corresponds to an integrated luminosity of 108.5 $pb^{-1}$ The measurement is compared to current phenomenology for vector boson production in proton-antiproton interactions, and the results are found to be consistent with expectation from Quantum Chromodynamics (QCD).
No description provided.
The two-jet differential cross section d3σ(p¯p→jet 1+jet 2+X)/dEtdη1dη2, averaged over -0.6≤η1≤0.6, at √s =1.8 TeV, has been measured in the Collider Detector at Fermilab. The predictions of leading-order quantum chromodynamics for most choices of structure functions show agreement with the data.
Systematic error contains all known systematic uncertainties, including the effect of uncertainties in the energy scale.
Systematic error contains all known systematic uncertainties, including the effect of uncertainties in the energy scale.
Systematic error contains all known systematic uncertainties, including the effect of uncertainties in the energy scale.
We present a measurement of the cross section for production of isolated prompt photons in p¯p collisions at √s =1.8 TeV. The cross section, measured as a function of transverse momentum (PT), agrees qualitatively with QCD calculations but has a steeper slope at low PT.
Additional normalization systematic uncertainty of 27 pct for first eleven entries, and +32 pct(-46 pct) for last four entries.
The charged-particle fractional momentum distribution within jets, D(z), has been measured in dijet events from 1.8-TeV p¯p collisions in the Collider Detector at Fermilab. As expected from scale breaking in quantum chromodynamics, the fragmentation function D(z) falls more steeply as dijet invariant mass increases from 60 to 200 GeV/c2. The average fraction of the jet momentum carried by charged particles is 0.65±0.02(stat)±0.08(syst).
No description provided.
Identified pi^[+/-] K^[+/-], p and p-bar transverse momentum spectra at mid-rapidity in sqrt(s_NN)=130 GeV Au-Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. The multiplicity densities scale faster than the number of participating nucleons. Kaon and nucleon yields per participant increase faster than the pion yields. In central collisions at high transverse momenta (p_T greater than 2 GeV/c), anti-proton and proton yields are comparable to the pion yields.
Transverse momentum spectra for PI+ in the midrapidity range for the centrality region 0 to 5 PCT. Errors are combined statistical and systematics.
Transverse momentum spectra for PI- in the midrapidity range for the centrality region 0 to 5 PCT. Errors are combined statistical and systematics.
Transverse momentum spectra for K+ in the midrapidity range for the centrality region 0 to 5 PCT. Errors are combined statistical and systematics.
Results on charged pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV are presented and compared to data at lower and higher energies. A rapid change of the energy dependence is observed around 30A GeV for the yields of pions and kaons as well as for the shape of the transverse mass spectra. The change is compatible with the prediction that the threshold for production of a state of deconfined matter at the early stage of the collisions is located at low SPS energies.
Transverse mass spectra for pion production in the central rapidity region for collisions at 20 GeV per nucleon.
Transverse mass spectra for pion production in the central rapidity region for collisions at 30 GeV per nucleon.
Transverse mass spectra for kaon production in the central rapidity region for collisions at 20 GeV per nucleon.
We have measured the ratios of antiparticles to particles for charged pions, kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) = 130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06 (syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.
130 GeV is sqrt(S) per nucleon-nucleon collision.
We present the first measurement of pseudorapidity densities of primary charged particles near mid-rapidity in Au+Au collisions at $\sqrt{s} =$ 56 and 130 AGeV. For the most central collisions, we find the charged particle pseudorapidity density to be $dN/d\eta |_{|\eta|<1} = 408 \pm 12 {(stat)} \pm 30 {(syst)}$ at 56 AGeV and $555 \pm 12 {(stat)} \pm 35 {(syst)}$ at 130 AGeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.
No description provided.
Diffractive scattering of $\gamma~* p \to X + N$, where $N$ is either a proton or a nucleonic system with $M_N<4$GeV has been measured in deep inelastic scattering (DIS) at HERA. The cross section was determined by a novel method as a function of the $\gamma~* p$ c.m. energy $W$ between 60 and 245GeV and of the mass $M_X$ of the system $X$ up to 15GeV at average $Q~2$ values of 14 and 31GeV$~2$. The diffractive cross section $d\sigma~{diff} /dM_X$ is, within errors, found to rise linearly with $W$. Parameterizing the $W$ dependence by the form $d\sigma~{diff}/dM_X \propto (W~2)~{(2\overline{\mbox{$\alpha_{_{I\hspace{-0.2em}P}}$}} -2)}$ the DIS data yield for the pomeron trajectory $\overline{\mbox{$\alpha_{_{I\hspace{-0.2em}P}}$}} = 1.23 \pm 0.02(stat) \pm 0.04 (syst)$ averaged over $t$ in the measured kinematic range assuming the longitudinal photon contribution to be zero. This value for the pomeron trajectory is substantially larger than $\overline{\mbox{$\alpha_{_{I\hspace{-0.2em}P}}$}}$ extracted from soft interactions. The value of $\overline{\mbox{$\alpha_{_{I\hspace{-0.2em}P}}$}}$ measured in this analysis suggests that a substantial part of the diffractive DIS cross section originates from processes which can be described by perturbative QCD. From the measured diffractive cross sections the diffractive structure function of the proton $F~{D(3)}_2(\beta,Q~2, \mbox{$x_{_{I\hspace{-0.2em}P}}$})$ has been determined, where $\beta$ is the momentum fraction of the struck quark in the pomeron. The form $F~{D(3)}_2 = constant \cdot (1/ \mbox{$x_{_{I\hspace{-0.2em}P}}$})~a$ gives a good fit to the data in all $\beta$ and $Q~2$ intervals with $a = 1.46 \pm 0.04 (stat) \pm
No description provided.
No description provided.
No description provided.
We report the first observation of charmed mesons with the ZEUS detector at HERA using the decay channel ${\rm D}~{*+}\rightarrow (\Do \rightarrow {\rm K}~-\pi~+)\pi~+$ (+ c.c.). Clear signals in the mass difference $\Delta M$=$M$(D$~*$)--$M$(D$~0)$ as well as in the $M(K\pi)$ distribution at the D$~0$ mass are found. The $ep$ cross section for inclusive \DSpm\ production with $Q~2<4\GeV~2$ in the $\gamma p$ centre-of-mass energy range $115 < W < 275$ \GeV\ has been determined to be $(32 \pm 7~{+4}_{-7} )$ nb in the kinematic region \mbox{\{$p_T(\DS)\geq $ 1.7 \,\GeV, $|\eta(\DS)| < 1.5 $\}}. Ex\-tra\-po\-la\-ting outside this region, assuming a mass of the charm quark of 1.5 \GeV, we estimate the $ep$ charm cross section to be $\sigma(e p \rightarrow c \bar{c}X ) = (0.45 \pm 0.11~{+0.37}_{-0.22}) \, \mu {\rm b} $ at \mbox{$\sqrt{s} = 296$}\GeV\ and $\langle W \rangle = 198$ \GeV. The average $\gamma p$ charm cross section \mbox{$\sigma(\gamma p \rightarrow c \bar{c}X )$} is found to be \mbox{$(6.3 \pm 2.2~{+6.3}_{-3.0}) \, \mu {\rm b} $} at $\langle W \rangle = 163$ \GeV\ and \mbox{$(16.9 \pm 5.2~{+13.9}_{-8.5}) \, \mu {\rm b} $} at $\langle W \rangle = 243$ \GeV. The increase of the total charm photoproduction cross section by one order of magnitude with respect to low energy data experiments is well described by QCD NLO calculations using singular gluon distributions in the proton.
No description provided.
Assumes probability of charmed quark pair fragmenting to D* is (55.2 +- 4.2) pct and mass of CQ is 1.5 GeV.
Assumes probability of charmed quark pair fragmenting to D* is (55.2 +- 4.2) pct and mass of CQ is 1.5 GeV.
We present a measurement of the inelastic, non diffractive J/$\psi$ photoproduction cross section in the reaction $e^{+} p \to e^{+} {J}/\psi X$ with the ZEUS detector at HERA. The J/$\psi$ was identified using both the $\mu^{+}\mu^{-}$ and $e^{+}e^{-}$ decay channels and events were selected within the range $0.4<z<0.9$ ($0.5<z<0.9$) for the muon (electron) decay mode, where $z$ is the fraction of the photon energy carried by the J/$\psi$ in the proton rest frame. The cross section, the $p^2_T$ and the $z$ distributions, after having subtracted the contributions from resolved photon and diffractive proton dissociative processes, are given for the photon-proton centre of mass energy range $50<W<180$ GeV; $p^2_T$ is the square of the J/$\psi$ transverse momentum with respect to the incoming proton beam direction. In the kinematic range $0.4 < z < 0.9$ and $p^2_T > 1$ GeV$^2$, NLO calculations of the photon-gluon fusion process based on the colour-singlet model are in good agreement with the data. The predictions of a specific leading order colour-octet model, as formulated to describe the CDF data on J/$\psi$ hadroproduction, are not consistent with the data.
Cross section for the MU+ MU- decay channel.
Cross section for the MU+ MU- decay channel.
Cross section for the MU+ MU- decay channel.
Forum