Scaled momentum distributions for the strange hadrons K0s and Lambda/bar Lambda were measured in deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 330 pb-1. The evolution of these distributions with the photon virtuality, Q2, was studied in the kinematic region 10<Q2<40000 GeV2 and 0.001<x<0.75, where x is the Bjorken scaling variable. Clear scaling violations are observed. Predictions based on different approaches to fragmentation were compared to the measurements. Leading-logarithm parton-shower Monte Carlo calculations interfaced to the Lund string fragmentation model describe the data reasonably well in the whole range measured. Next-to-leading-order QCD calculations based on fragmentation functions, FFs, extracted from e+e- data alone, fail to describe the measurements. The calculations based on FFs extracted from a global analysis including e+e-, ep and pp data give an improved description. The measurements presented in this paper have the potential to further constrain the FFs of quarks, anti-quarks and gluons yielding K0s and Lambda/bar Lambda strange hadrons.
The measured scaled momentum distributions for K0S production as a function of Q^2 in three XP regions.
The measured scaled momentum distributions for K0S production as a function of Q^2 in six XP regions.
The measured scaled momentum distributions for K0S production as a function of Q^2 in three XP regions.
This paper presents measurements of \k\ and \lam\ production in neutral current, deep inelastic scattering of 26.7 GeV electrons and 820 GeV protons in the kinematic range $ 10 < Q~{2} < 640 $ GeV$~2$, $0.0003 < x < 0.01$, and $y > 0.04$. Average multiplicities for \k\ and \lam\ production are determined for transverse momenta \ \ptr\ $> 0.5 $ GeV and pseudorapidities $\left| \eta \right| < 1.3$. The multiplicities favour a stronger strange to light quark suppression in the fragmentation chain than found in $e~+ e~-$ experiments. The production properties of \k's in events with and without a large rapidity gap with respect to the proton direction are compared. The ratio of neutral \k's to charged particles per event in the measured kinematic range is, within the present statistics, the same in both samples.
No description provided.
No description provided.
No description provided.
We report on the measurement of the Central Exclusive Production of charged particle pairs $h^{+}h^{-}$ ($h = \pi, K, p$) with the STAR detector at RHIC in proton-proton collisions at $\sqrt{s} = 200$ GeV. The charged particle pairs produced in the reaction $pp\to p^\prime+h^{+}h^{-}+p^\prime$ are reconstructed from the tracks in the central detector, while the forward-scattered protons are measured in the Roman Pot system. Differential cross sections are measured in the fiducial region, which roughly corresponds to the square of the four-momentum transfers at the proton vertices in the range $0.04~\mbox{GeV}^2 < -t_1 , -t_2 < 0.2~\mbox{GeV}^2$, invariant masses of the charged particle pairs up to a few GeV and pseudorapidities of the centrally-produced hadrons in the range $|\eta|<0.7$. The measured cross sections are compared to phenomenological predictions based on the Double Pomeron Exchange (DPE) model. Structures observed in the mass spectra of $\pi^{+}\pi^{-}$ and $K^{+}K^{-}$ pairs are consistent with the DPE model, while angular distributions of pions suggest a dominant spin-0 contribution to $\pi^{+}\pi^{-}$ production. The fiducial $\pi^+\pi^-$ cross section is extrapolated to the Lorentz-invariant region, which allows decomposition of the invariant mass spectrum into continuum and resonant contributions. The extrapolated cross section is well described by the continuum production and at least three resonances, the $f_0(980)$, $f_2(1270)$ and $f_0(1500)$, with a possible small contribution from the $f_0(1370)$. Fits to the extrapolated differential cross section as a function of $t_1$ and $t_2$ enable extraction of the exponential slope parameters in several bins of the invariant mass of $\pi^+\pi^-$ pairs. These parameters are sensitive to the size of the interaction region.
Differential fiducial cross section for CEP of $\pi^+\pi^-$ pairs as a function of the invariant mass of the pair. Systematic uncertainties assigned to data points are strongly correlated between bins and should be treated as allowed collective variation of all data points. There are two components of the total systematic uncertainty. The systematic uncertainty related to the experimental tools and analysis method is labeled "syst. (experimental)". The systematic uncertainty related to the integrated luminosity (fully correlated between all data points) is labeled "syst. (luminosity)". Fiducial region definition: * central state $\pi^+$, $\pi^-$ - $p_{\mathrm{T}} > 0.2~\mathrm{GeV}$ - $|\eta| < 0.7$ * intact forward-scattered beam protons $p'$ - $p_x > -0.2~\mathrm{GeV}$ - $0.2~\mathrm{GeV} < |p_{y}| < 0.4~\mathrm{GeV}$ - $(p_x+0.3~\mathrm{GeV})^2 + p_y^2 < 0.25~\mathrm{GeV}^2$
Differential fiducial cross section for CEP of $K^+K^-$ pairs as a function of the invariant mass of the pair. Systematic uncertainties assigned to data points are strongly correlated between bins and should be treated as allowed collective variation of all data points. There are two components of the total systematic uncertainty. The systematic uncertainty related to the experimental tools and analysis method is labeled "syst. (experimental)". The systematic uncertainty related to the integrated luminosity (fully correlated between all data points) is labeled "syst. (luminosity)". Fiducial region definition: * central state $K^+$, $K^-$ - $p_{\mathrm{T}} > 0.3~\mathrm{GeV}$ - $min(p_{\mathrm{T}}(K^+), p_{\mathrm{T}}(K^-)) < 0.7~\mathrm{GeV}$ - $|\eta| < 0.7$ * intact forward-scattered beam protons $p'$ - $p_x > -0.2~\mathrm{GeV}$ - $0.2~\mathrm{GeV} < |p_{y}| < 0.4~\mathrm{GeV}$ - $(p_x+0.3~\mathrm{GeV})^2 + p_y^2 < 0.25~\mathrm{GeV}^2$
Differential fiducial cross section for CEP of $p\bar{p}$ pairs as a function of the invariant mass of the pair. Systematic uncertainties assigned to data points are strongly correlated between bins and should be treated as allowed collective variation of all data points. There are two components of the total systematic uncertainty. The systematic uncertainty related to the experimental tools and analysis method is labeled "syst. (experimental)". The systematic uncertainty related to the integrated luminosity (fully correlated between all data points) is labeled "syst. (luminosity)". Fiducial region definition: * central state $p$, $\bar{p}$ - $p_{\mathrm{T}} > 0.4~\mathrm{GeV}$ - $min(p_{\mathrm{T}}(p), p_{\mathrm{T}}(\bar{p})) < 1.1~\mathrm{GeV}$ - $|\eta| < 0.7$ * intact forward-scattered beam protons $p'$ - $p_x > -0.2~\mathrm{GeV}$ - $0.2~\mathrm{GeV} < |p_{y}| < 0.4~\mathrm{GeV}$ - $(p_x+0.3~\mathrm{GeV})^2 + p_y^2 < 0.25~\mathrm{GeV}^2$
The $\bar{\Lambda} / \Lambda$ and $\bar{\Lambda} / K^0_\mathrm{S}$ production ratios are measured by the LHCb detector from $0.3\,\mathrm{nb}^{-1}$ of $pp$ collisions delivered by the LHC at $\sqrt{s} = 0.9$\,TeV and $1.8\,\mathrm{nb}^{-1}$ at $\sqrt{s} = 7$\,TeV. Both ratios are presented as a function of transverse momentum, $p_\mathrm{T}$, and rapidity, $y$, in the ranges {$0.15 < p_\mathrm{T} < 2.50\,\mathrm{GeV}/c$} and {$2.0<y<4.5$}. Results at the two energies are in good agreement as a function of rapidity loss, $\Delta y = y_\mathrm{beam} - y$, and are consistent with previous measurements. The ratio $\bar{\Lambda} / \Lambda$, measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted in simulation, particularly at high rapidity. The ratio $\bar{\Lambda} / K^0_\mathrm{S}$, measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected.
Lambdabar over Lambda @ 900GeV in y interals for (0.25<PT<0.65),(0.65<PT<1.00),(1.00<PT<2.50) GeV/c.
$\bar{\Lambda}$ to $\Lambda$ production ratio in $pp$ collisions at 900 GeV in $y$ intervals for ($0.25 < p_T < 0.65$), ($0.65 < p_T < 1.00$), ($1.00 < p_T < 2.50$) GeV$/c$.
Lambdabar over K0s @ 900GeV in y interals for (0.25<PT<0.65),(0.65<PT<1.00),(1.00<PT<2.50) GeV/c.
We report on a study of inclusive particle production in pp-interactions at 400 GeV/c. The data are based on 472 K reconstructed events recorded in the NA 27 experiment using the LEBC-EHS facility at CERN. The production cross sections are determined of pseudo scalar (π±,0, η andK±), scalar (f0(975)), vector (ρ±,0(770), ω(783), ϕ(1020),K*0(892), and\(\bar K^{ * 0} \)(892)), and tensorf0 mesons, of protons and antiprotons, and theΔ++,+,0(1232), and Λ(1520) baryon resonances in the forward hemisphere of the center of mass system, as well as longitudinal and transverse momentum distributions. The results are compared with predictions of the FRITIOF model and with other experimental data.
No description provided.
No description provided.
No description provided.
Inclusive and semi-inclusive production of Λ and\(\bar \Lambda\) inK+p interactions is studied at an incident momentum of 70 GeV/c. Cross sections and single particle distributions are presented and compared with data at lower energies. Scaling is observed between 32 and 70 GeV/c in the Feynmanx variable in the target and the beam fragmentation regions for Λ and\(\bar \Lambda\) inclusive production respectively. An increase of Λ (\(\bar \Lambda\)) production is observed in the beam (target) fragmentation regions, whereas the data at 70 and 32 GeV/c are reasonably close in the central region. The dependence of the Λ(\(\bar \Lambda\)) polarization as a function ofx is measured and found to be in general agreement with the results at 32 GeV/c. The (Λ\(\bar \Lambda\)) pair production cross section increases significantly from 32 to 70 GeV/c. The Λ and\(\bar \Lambda\) production associated with an identified proton is also studied.
No description provided.
No description provided.
No description provided.
The production cross sections for the Λ, Σ0, Ξ−, Σ0 (1385), Ξ0 (1530) and Ω− hyperons have been measured, both in the continuum and in direct ϒ decays. Baryon rates in direct ϒ decays are enhanced by a factor of 2.5 or more compared to the continuum. Such a large baryon enhancement cannot be explained by standard fragmentation models. The strangeness suppression for baryons and mesons turns out to be the same. A strong suppression of spin 3/2 states is observed.
Hyperon rates per multihadronic event in direct UPSILON decays.
Hyperon rates per multihadronic event in the continuum.
LAMBDA spectrum (1/SIG(had))*D(SIG)/D(X) for UPSILON (1S) direct decays, with X = P/Pmax.
The experimentally determined average charged-particle multiplicities, 〈nX〉, of the systems, X, produced in the following reactions for 147 GeV/c incident pion momentum are presented as functions of the square of the invariant mass of X, MX2, and of |t|:π−p→πfast−X, π−p→pX, π−p→Δ++X, π−p→(π−π+)ρ0X, and π−p→Λ0X. Details of the analysis are discussed. These data can be fit by the expression 〈nX〉=A+B ln MX2+C|t| and the coefficients obtained for B are equal within their uncertainties. C is significantly different from zero only for π−p→πfast−X. These results and 〈nX〉 data from other inclusive and total-inelastic-reaction studies are discussed in terms of a simple model which assumes contributions to 〈nX〉 from the target-fragmentation, the central, and the beam-fragmentation regions in the case of total-inelastic reactions. For inclusive reactions, either the beam or target fragmentation is replaced by an exchange-particle-fragmentation contribution. The s, t, and MX2 dependence of the parameters of the model are deduced from triple-Regge considerations. The data are found to be consistent with the model and values are presented for the parameters.
No description provided.
No description provided.
We use 772$\times 10^6$ $B \bar{B}$ meson pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector to measure the branching fraction for $\bar{B} \rightarrow X_s \gamma$. Our measurement uses a sum-of-exclusives approach in which 38 of the hadronic final states with strangeness equal to $+1$, denoted by $X_s$, are reconstructed. The inclusive branching fraction for $M_{X_s}<$ 2.8 GeV/$c^2$, which corresponds to a minimum photon energy of 1.9 GeV, is measured to be ${\cal B}(\bar{B} \rightarrow X_s \gamma)=(3.51\pm0.17\pm0.33)\times10^{-4}$, where the first uncertainty is statistical and the second is systematic.
The yields and partial branching fraction in each $M_{X_s}$ mass bin for the decay $\bar{B} \rightarrow X_s \gamma$, where $\bar{B}$ is either $\bar{B}^0$ or $B^-$, $X_s$ denotes all the hadron combinations that carry strangeness of +1, and charge conjugation is implied.
The angular distributions and the differential branching fraction of the decay B0 to K*0(892) mu mu are studied using data corresponding to an integrated luminosity of 20.5 inverse femtobarns collected with the CMS detector at the LHC in pp collisions at sqrt(s) = 8 TeV. From 1430 signal decays, the forward-backward asymmetry of the muons, the K*0(892) longitudinal polarization fraction, and the differential branching fraction are determined as a function of the dimuon invariant mass squared. The measurements are among the most precise to date and are in good agreement with standard model predictions.
The measured values of signal yield, FL, AFB, and differential branching fraction in bins of the dimuon invariant mass squared. The (FL,AFB) correlation factors are also shown.
The measured values of FL, AFB, and differential branching fraction in bins of the dimuon invariant mass squared, combining the 7 TeV and 8 TeV results.
Forum