Tensor Meson Production Research Articles

Production of f2(1270) meson in pp collisions at the LHC via gluon-gluon fusion in the kt-factorization approach

We calculate inclusive cross section for f2(1270) tensor meson production via color singlet gluon-gluon fusion in the kt-factorization approach with unintegrated gluon distribution functions (UGDFs). The process may be potentially interesting in the context of searches for saturation effects. The energy-momentum tensor, equivalent to helicity-2 coupling, and helicity-0 coupling are used for the g⁎g⁎→f2(1270) vertex. Two somewhat different parametrizations of helicity-2 and helicity-0 tensorial structure from the literature are used in our calculations. Some parameters are extracted from γγ→f2(1270)→ππ reactions. Different modern UGDFs from the literature are used. The results strongly depend on the parametrization of the g⁎g⁎→f2(1270) form factor. Our results for transverse momentum distributions of f2 are compared to preliminary ALICE data. We can obtain agreement with the data only at larger f2(1270) transverse momenta only for some parametrizations of the g⁎g⁎→f2(1270) form factor. No obvious sign of the onset of saturation is possible. At low transverse momenta one needs to include also the ππ final-state rescattering. The agreement with the ALICE data can be obtained by adjusting probability of formation and survival of f2(1270) in a harsh quark-gluon and multipion environment. The pomeron-pomeron fusion mechanism is discussed in addition and results are quantified.

Role of QCD compositeness in the production of scalar and tensor mesons through single-photon annihilation e+e−→γ*→γS(T)

We study the exclusive production of scalar $S = 0^{++}$ and tensor $T = 2^{++}$ mesons through single-photon annihilation $e^+ e^- \to \gamma^* \to \gamma S(T)$. Using QCD compositeness of the involved hadrons considered as quark-antiquark systems, the prediction for the scaling of the differential cross sections of these processes is $d\sigma/dt \sim 1/s^3$ at large $s$. We further derive the scaling of the $\gamma^\ast \to \gamma S$ and $\gamma^\ast \to \gamma T$ transition form factors: $F_{\gamma^\ast\gamma S}(s) \sim 1/s$ and $F_{\gamma^\ast\gamma T}(s) \sim 1/s^2$. Results for the respective cross sections of the scalar and tensor meson production are presented. Note, when scalar and tensor mesons are considered as tetraquark systems of two tightly bound color diquarks, corresponding to them transition form factors and differential cross sections have the same falloffs as in case of quark-antiquark picture. For other tetraquark or two-hadron molecules configurations the transition form factors $F_{\gamma^\ast\gamma S(T)}(s)$ and the differential cross section $d\sigma/dt$ have additional $1/s$ and $1/s^2$ falloffs, respectively.

Electroproduction of tensor mesons in QCD

Due to multiple possible polarizations hard exclusive production of tensor mesons by virtual photons or in heavy meson decays offers interesting possibilities to study the helicity structure of the underlying short-distance process. Motivated by the first measurement of the transition form factor $\gamma^*\gamma \to f_2(1270)$ at large momentum transfers by the BELLE collaboration we present an improved QCD analysis of this reaction in the framework of collinear factorization including contributions of twist-three quark-antiquark-gluon operators and an estimate of soft end-point corrections using light-cone sum rules. The results appear to be in a very good agreement with the data, in particular the predicted scaling behavior is reproduced in all cases.

Comparative study of the scalar- and tensor-meson production in the reaction γγ * (Q 2)→ ηπ 0

The prediction of the cross section $\sigma(\gamma\gamma^*(Q^2)\to \eta\pi^0)$ based on the simultaneous description of the Belle data on the $\gamma\gamma\to \eta\pi^0$ reaction and the KLOE data on the $\phi\to\eta\pi^0\gamma$ decay is presented. The production of the scalar $a_0(980)$ and tensor $a_2(1320)$ is studied in detail. It is shown that the QCD based asymptotics of the $\gamma^*(Q^2)\gamma\to a_2(1320)\to\eta\pi^0$ cross section can be reached by the compensation of the contributions of $\rho(770)$ and $\omega(782)$ with the contributions of their radial excitations in $Q^2$ channel. At large $Q^2$ the $a_2(1320)$ contribution is expected to be dominant, while at $Q^2=0$ it is similar to the scalars contribution.

Central exclusive diffractive production of theπ+π−continuum, scalar, and tensor resonances inppandpp¯scattering within the tensor Pomeron approach

We consider central exclusive diffractive dipion production in the reactions $pp \to pp \pi^{+} \pi^{-}$ and $p\bar{p} \to p\bar{p} \pi^{+} \pi^{-}$ at high energies. We include the dipion continuum, the dominant scalar $f_{0}(500)$, $f_{0}(980)$, and tensor $f_{2}(1270)$ resonances decaying into the $\pi^{+} \pi^{-}$ pairs. The calculation is based on a tensor pomeron model and the amplitudes for the processes are formulated in terms of vertices respecting the standard crossing and charge-conjugation relations of Quantum Field Theory. The formulae for the dipion continuum and tensor meson production are given here for the first time. The theoretical results are compared with existing STAR, CDF, CMS experimental data and predictions for planned or being carried out experiments (ALICE, ATLAS) are presented. We show the influence of the experimental cuts on the integrated cross section and on various differential distributions for outgoing particles. Distributions in rapidities and transverse momenta of outgoing protons and pions as well as correlations in azimuthal angle between them are presented. We find that the relative contribution of resonant $f_2(1270)$ and dipion continuum strongly depends on the cut on proton transverse momenta or four-momentum transfer squared $t_{1,2}$ which may explain some controversial observations made by different ISR experiments in the past. The cuts may play then the role of a $\pi \pi$ resonance filter. We suggest some experimental analyses to fix model parameters related to the pomeron-pomeron-$f_{2}$ coupling.

Comparative study of the production of scalar and tensor mesons ine+e−collisions

The intensity of scalar $a_0(980)$, $f_0(980)$ and tensor $a_2(1320)$, $f_2(1270)$ mesons production at VEPP-2000 (BINP, Novosibirsk) and the upgraded DA$\Phi$NE (Frascati, Italy) in the processes $e^+e^- \to a_0 (f_0$, $a_2$, $f_2) \gamma$ is calculated. The calculation was made with the help of VDM and the kaon loop model (for scalar mesons case). Note that the processes $e^+e^-\to a_2(f_2)\gamma$ have not been studied in the energy region of VEPP-2000. It turned out that in the VEPP-2000 energy region $1.7-2.0$ GeV $\sigma(e^+e^-\to a_2(f_2)\gamma)\sim 10$ pb, and $\sigma(e^+e^-\to a_0(f_0)\gamma)\sim 0.1$ pb. Photon angle distribution and the spin density matrices of $a_2$ and $f_2$ were calculated also.

Tensor meson production in proton-proton collisions from the color glass condensate

We compute the inclusive cross section of ${f}_{2}$ tensor-meson production in proton-proton collisions at high energy. We use an effective theory inspired from the tensor-meson dominance hypothesis that couples gluons to ${f}_{2}$ mesons. We compute the differential cross section in the ${k}_{\ensuremath{\perp}}$ factorization and in the color glass condensate formalism in the low density regime. We show that the two formalisms are equivalent for this specific observable. Finally, we study the phenomenology of ${f}_{2}$ mesons by comparing theoretical predictions of different parametrizations of the unintegrated gluon distribution function. We find that ${f}_{2}$-meson production is another observable that can be used to put constraints on these distributions.

Proton-Antiproton annihilation at 900 MeV/c into $\pi^0\pi^0\pi^0, \pi^0\pi^0\eta$ and $\pi^0\eta\eta$

The three reactions $\overline{p}p \rightarrow \pi^0\pi^0\pi^0$ , $\pi^0\pi^0\eta$ and $\pi^0\eta\eta$ in proton-antiproton annihilation in flight at 900 MeV/c are used to search for isoscalar $0^{++}$ and $2^{++}$ mesons in the mass range 1000–2000 MeV, in particular the $f_0(1710)$ . The description of both $\pi^0\pi^0\pi^0$ and $\pi^0\eta\eta$ data sets requires an isoscalar tensor resonance decaying into $\pi^0\pi^0$ and $\eta\eta$ with a mass of $(1867\pm46)$ MeV and a width of $(385\pm58)$ MeV. The ratio of partial widths $\Gamma(\eta\eta)/\Gamma(\pi\pi)$ is $0.27 \pm 0.10$ . The analyses of both $\pi^0\pi^0\pi^0$ and $\pi^0\eta\eta$ show no signal for the $f_0(1710)$ . The $\pi^0\eta\eta$ data set shows a strong signal of the $f_2^{\prime}(1525)$ suggesting a large OZI rule violation for tensor meson production in $\overline{p}p$ annihilation. The $\pi^0\pi^0\pi^0$ data set also requires the $f_2(1565)$ . The signal for the $f_2(1810)$ reported by earlier experiments is confirmed neither in $\pi^0\pi^0\pi^0$ nor in $\pi^0\eta\eta$ . The analysis of $\pi^0\pi^0\eta$ leads to an isovector tensor state decaying into $\pi^0\eta$ with a mass of $(1698\pm44)$ MeV and a width of $(265\pm55)$ MeV.

Hard exclusive production of tensor mesons

We point out that hard exclusive production of tensor mesons f 2(1270) with helicity λ=±2 is dominated by the gluon component in the meson wave function and can be used to determine gluon admixture in tensor mesons in a theoretically clean manner. We present a detailed analysis of the tensor meson distribution amplitudes and calculate the transition form factor γ+γ ∗→f 2(1270) for one real and one virtual photon.

Hyperfine splitting in light-flavour hadron production at LEP

The production rates of light-flavour hadrons at LEP 1 are set by their masses, spins, strangeness suppression, and strongly influenced by the spin-spin interactions of their quarks. Similarities in production of pseudoscalar mesons and octet baryons, vector mesons and decuplet baryons are observed and explained by the relative spin configurations of their quarks. Similarity in production of tensor mesons and Λ(1520) is also seen. The vector-to-pseudoscalar meson and decuplet-to-octet baryon suppressions are the same and explained by the hyperfine mass splitting. The strangeness suppression factor, λ=0.295±0.006, is the same for mesons and baryons. It is related to the difference in the constituent quark masses, λ= e −(m s− m ̂ )/T , where m ̂ =m u=m d , at the temperature, T=142.4±1.8 MeV/ c 2. No evidence for additional suppression of strange baryons is observed. The LEP 1 data are compared with hadronic reactions and heavy nuclear collisions.

Study of φ and f′ 2(1525) meson production in [formula omitted] annihilation at rest

The reaction p ̄ p→K +K −π 0 was analysed for antiproton annihilations at rest at three hydrogen target densities. A strong dependence of the p ̄ p→φπ 0 yield on the quantum numbers of the initial state is observed. The branching ratio of the φπ 0 channel from the 3 S 1 initial state is more than 15 times larger than the one from the 1 P 1 state. A large apparent violation of the OZI rule for tensor meson production from p ̄ p -annihilations from the P-waves (1 +++2 ++) is observed: R exp( f′ 2 π 0/ f 2 π 0)=(149±20)·10 −3, significantly exceeding the OZI-rule prediction R=16·10 −3.

Study of the weak charged hadronic current in b decays

Charged and neutral particle multiplicities of jets associated with identified semileptonic and hadronic b decays are studied. The observed differences between these jets are used to determine the inclusive properties of the weak charged hadronic current. The average charged particle multiplicity of the weak charged hadronic current in b decays is measured for the first time to be 2.69±0.07(stat.)±0.14(syst.). This result is in good agreement with the JETSET hadronization model of the weak charged hadronic current if 40±17% of the produced mesons are light-flavored tensor (L=1) mesons. This level of tensor meson production is consistent with the measurement of the π 0 multiplicity in the weak charged hadronic current in b decays.

Inclusive strange vector and tensor meson production in hadronic Z0 decays

Measurements have been made in the OPAL experiment at LEP of the inclusive production of strange vector φ(1020) and K*(892)0 mesons, and the tensor meson K *2 (1430)0. The overall production rates per hadronic Z0 decay have been determined to be 0.100±0.004stat.±0.007syst. φ(1020) mesons, 0.74±0.03stat.±0.03syst. K*(892)0 mesons and (forx E <0.3) 0.19±0.04stat.±0.06syst. K *2 (1430)0 mesons. The measurements for the vector states update previously published results based on lower statistics, while the K *2 (1430)0 rate represents the first direct measurement of a strange tensor state in Z0 decay. For the vector states, both the overall production rates and normalised differential cross sections, with respect to the scaled energy variablex E , have been compared to JETSET and HERWIG predictions. The peak positions in the ζ=ln(1/x p ) distributions have been measured and compared to measurements of other hadron states.

Semihard production of neutral pseudoscalar and tensor mesons in photon-photon collisions

We investigate the semihard production of neutral pseudoscalar and tensor mesons in high-energy γγ collisions (M = P = π 0, η, η′ or M = T = a 2, f 2, f′ 2). We deal with the exclusive γγ → MM′ or semi-exclusive γγ → MX reactions (X is the hadron jet with not too large mass). The considered transfer momenta are small in comparison with the photon energies and they are large in comparison with the confinement scale. The amplitudes of these processes are determined by the odderon exchange, i.e. three-gluon exchange in the lowest order of perturbative QCD. The cross sections are calculated in this approximation. The possibility of measurements at LEP and at future γγ colliders is discussed.

Vector and tensor meson production in ϒN processes in the backward directionprocesses in the backward direction

Backward high-energy vector and tensor meson production is studied in an effective pole molde withNαNγ and Δδ effective poles. In order to explain the ω0-production dip in dσ/du, the isoscalar photon isospin-1/2 coupling is found to play a crucial role in our parametrization. Further experiments are suggested.

Production of vector and tensor mesons in proton-proton collisions at $$\sqrt s = 52.5$$ GeV

Inclusive production of ϱ0,f, andg 0 mesons and ofK 0 ,K *0 (892), ϕ andK *0(1430)mesons has been measured at ∼2.6 and <p T >∼1.1 GeV/c in proton-proton interactions at $$\sqrt s = 52.5$$ GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andp T dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.

Tensor meson production in photon-photon collisions

Recent work on the electromagnetic properties of tensor mesons is extended to their production in e+e- collisions via the two-photon process. It is shown how the model proposed can be tested experimentally.

Backward axial vector meson production at intermediate energy

We analyse the recent data on backward axial vector meson production which come predominantly from a large K −p bubble chamber experiment at 4.2 GeV/ c. In an attempt to understand the production mechanisms, we study the isospin and SU(3) structure of A 1, B, D(1285) and C(1280) production and compare this with the corresponding production of pseudoscalar, vector and tensor mesons in the backward direction. The isospin and SU(3) study shows that octet exchange is dominant but there are indications that other exchanges, lower-lying than the nucleon (N α) trajectory, must also be important. We show that a consistent description of backward resonance production is possible, but further experiments are required to confirm this.

Vector and tensor meson production in K −p interactions at 32 GeV/ c

Inclusive production of vector and tensor mesons is studied in a K −p experiment at 32 GeV/ c in the MIRABELLE bubble chamber. The K ∗ 0 (890) , ϱ 0 and ω cross sections are comparable, about 4 mb each. The K ∗ 0 (1420 and cross sections are also comparable, about 1 mb each. The K ∗ o ̈ + (890), Φ, K ∗ o ̈ − (1420) and f cross sections beam fragmentation; ϱ production is almost forward-backward symmetric in the c.m.s. The p T production slopes of K ∗ o ̈ − (890) and ϱ are similar, the Φ slope is shallower. Vector and tensor mesons alone are responsible for ≅50% (≅60%) of final-state pions

Inclusive production of vector and tensor mesons in antiproton-proton annihilation and non-annihilation interactions at 9.1 GeV/c

Cross sections have been determined for the inclusive production of vector (ϱ 0, ω, K ∗) and tensor (f, A 2 ±) mesons in pp reactions at 9.1 GeV/c for both annihilation and non-annihilation processes. Distributions in the Feynman variable x and transverse momentum squared, p T 2, have been examined for the ϱ 0, ω and f mesons. The slopes for p T 2 appear to be exponential and decrease with increasing particle mass for both annihilation and non-annihilation reactions, furthermore the slopes have consistently higher values for non-annihilation reactions. Comparisons with other data indicate that the ratio ϱ 0/ π − is independent of antiproton momentum in annihilation processes.