Details of the analysis of the ηπ system studied in the reaction πp → ηπp at 18 GeV/c are given. Separate analyses for the 2γ and π+π−π0 decay modes of the η are presented. An amplitude analysis of the data indicates the presence of interference between the a−2 (1320) and a J PC = 1−+ wave between 1.2 and 1.6 GeV/c2. The phase difference between these waves shows phase motion not attributable solely to the a−2 (1320). The data can be fitted by interference between the a−2 (1320) and an exotic 1−+ resonance with M = (1370 ±16 +50 −30 ) MeV/c 2 and Γ = (385 ±40 +65 −105 ) MeV/c 2. Our results are compared with those of other experiments. Typeset using REVTEX

The ηπ system has been studied in the reaction πp → ηπp at 18 GeV/c. A large asymmetry in the angular distribution is observed indicating interference between L-even and L-odd partial waves. The a2(1320) is observed in the J = 2 wave, as is a broad enhancement between 1.2 and 1.6 GeV/c in the 1 wave. The observed phase difference between these waves shows that there is phase motion in addition to that due to a2(1320) decay. The data can be fitted by interference between the a2(1320) and an exotic 1 −+ resonance with M = (1370 ±16 +50 −30 ) MeV/c and Γ = (385 ±40 +65 −105 ) MeV/c. 13.60.Le, 13.85.Fb, 14.40.Cs Typeset using REVTEX 2 The question of whether or not hadrons outside the scope of the constituent quark model exist is one whose answer speaks directly to the fullness of our understanding of quantum chromodynamics (QCD) [1]. However, non-qq mesons (or exotic mesons) have proven difficult to distinguish from the many conventional qq states which populate the various mesonic spectra. For this reason, much attention has been focused on those states with manifestly exotic J quantum numbers. A qq meson with orbital angular momentum l and total spin s must have P = (−1) and C = (−1). Thus a resonance with J = 0, 0, 1, 2, ... must be exotic. Such a state could be a gluonic excitation such as a hybrid (qqg) or glueball (2g, 3g, ...), or a multiquark (qqqq) state. In a relative P wave (L=1), the ηπ system has J = 1. Having isospin I=1, it could not be a glueball, but it could be a hybrid or a multiquark state. Production and decay properties of exotic states have been predicted using several models [2–8]. A calculation based upon the MIT bag model predicts [3] that a 1 hybrid (qqg) will have a mass near 1.4 GeV/c. On the other hand, the flux-tube model [4,5] predicts the mass of the lowest-lying hybrid state to be around 1.8 GeV/c. Characteristics of bag-model S-wave multiquark states (which would have J = 0, 1, or 2) have been predicted [7] but those for a 1 state have not. Finally, recent lattice calculations [8] of the 1 hybrid meson estimate its mass to be in the range of 1.7 to 2.1 GeV. The ηπ system has been studied in several recent experiments, with apparently inconsistent results. Alde et al. [9], in a study of πp interactions at 100 GeV/c at CERN (the GAMS experiment), claimed to observe a 1 state in the ηπ system at 1.4 GeV/c produced via unnatural parity exchange (the P0 partial wave—the naming convention is discussed below) [10]. Aoyagi et al. [11], in a πp experiment at 6.3 GeV/c at KEK, observed a rather narrow enhancement in the ηπ system at 1.3 GeV/c in the natural parity exchange 1 spectrum (P+). Beladidze et al. [12], in the VES experiment at IHEP, (π N interactions at 37 GeV/c) also reported a P+ signal in the ηπ − state, but their signal was broader and had a significantly different phase variation from that of the KEK experiment. While the 3 phase difference between the P+ and D+ waves was independent of ηπ mass in the KEK analysis, that phase difference did show significant mass dependence in the VES analysis. (Since the phase variation for the D+ wave follows a classic Breit-Wigner pattern for the a2(1320) meson, the phase difference between these waves can determine the phase variation of the unknown P+ wave.) Here we study the ηπ system in the reaction πp → ηπp at 18 GeV/c. Our data sample was collected in the first data run of E852 at the AGS at Brookhaven National Laboratory with the Multi-Particle Spectrometer (MPS) [13] using a liquid hydrogen target. The MPS, which was equipped with six drift-chamber modules [14] and three proportional wire chambers, was augmented by: a four-layer cylindrical drift chamber surrounding the target [15]; a soft-photon detector consisting of 198 blocks of thallium-doped cesium iodide [16] also surrounding the target; a window-frame lead-scintillator photon-veto counter; a large drift chamber; and a 3045-element lead-glass detector (LGD) [17] downstream of the MPS. Further details are given elsewhere [18]. A total of 47 million triggers which required one forward-going charged track, one recoil charged track, and an LGD trigger-processor signal enhancing high electromagnetic effective mass was recorded. Of these, 47,200 events were reconstructed which were consistent with the ηπp (η → 2γ) final state. These events satisfied topological and fiducial volume cuts, as well as energy/momentum conservation for production and for the η → 2γ decay with a confidence level > 10% [19]. The 2γ mass resolution at the η mass is σ = 0.03 GeV/c. The a2(1320) is the dominant feature of the ηπ − mass spectrum shown in Fig. 1a. Background has been estimated using side bands in both the 2-γ mass distribution and the missing-mass distribution, thus taking into account background from non-η sources as well as from sources due to production of other final states. The background level is approximately 7% at 1.2 GeV/c, falling to 1% at 1.3 GeV/c. The acceptance-corrected distribution of |t| = |t| − |t|min, where t is the the fourmomentum-transfer, is shown for |t| > 0.08(GeV/c) in Fig. 1b. (Our acceptance is quite low below 0.08 (GeV/c) due to a trigger requirement.) The shape of this distribution is con4 sistent with previous experiments and has been shown to be consistent with natural-parity exchange production in Regge-pole phenomenology [20,21]. The acceptance-corrected distribution of cos θ, the cosine of the angle between the η and the beam track in the Gottfried-Jackson frame [22] of the ηπ system, is shown in Fig. 2a for 1.22 < M(ηπ) < 1.42 GeV/c. There is a forward-backward asymmetry in cos θ. The asymmetry for | cos θ| < 0.8 is plotted as a function of ηπ mass in Fig. 2b. The asymmetry is large, statistically significant and mass dependent. Since the presence of only even values of L would yield a symmetric distribution in cos θ, the observed asymmetry requires that odd-L partial waves be present to describe the data. A partial-wave analysis (PWA) [23,24] based on the extended maximum likelihood method has been used to study the spin-parity structure of the ηπ system. The partial waves are parameterized in terms of the quantum numbers J as well as m, the absolute value of the angular momentum projection, and the reflectivity ǫ (which is positive (negative) for natural (unnatural) parity exchange [25]). In our naming convention, a letter indicates the angular momentum of the partial wave in standard spectroscopic notation, while a subscript of 0 means m = 0, ǫ = −1, and a subscript of +(−) means m = 1, ǫ = +1(−1). Thus, S0 denotes the partial wave having J m = 00, while P− signifies 11, D+ means 2 1, and so on. We consider partial waves with m ≤ 1, and we assume that the production spin-density matrix has rank one. The experimental acceptance is determined by a Monte Carlo method. Peripherallyproduced events are generated [26] with isotropic angular distributions in the GottfriedJackson frame. After adding detector simulation [27], the Monte Carlo event sample is subjected to the same event-selection cuts and run through the same analysis as the data. The experimental acceptance is then incorporated into the PWA by using these events to calculate normalization integrals (see ref. [23]). Goodness-of-fit is determined by calculation of a χ from comparison of the experimental moments with those predicted by the results of the PWA fit. A systematic study has been performed to determine the effect on goodness-of-fit of adding and subtracting partial waves 5 of J ≤ 2 and m ≤ 1. All such waves have been included in the final fit. We have also performed fits including partial waves with J = 3 and J = 4. Contributions from these partial waves are found to be insignificant for M(ηπ) < 1.8 GeV/c. Thus, PWA fits shown or referred to in this letter include all partial waves with J ≤ 2 and m ≤ 1 (i.e. S0, P0, P−, D0, D−, P+, and D+). The background described above was included as a non-interfering, isotropic term of fixed magnitude. The results of the PWA fit in 40 MeV/c bins for 0.98 < M(ηπ) < 1.82 GeV/c and 0.10 < |t| < 0.95 GeV are shown in Fig. 3a-c. Here, the acceptance-corrected numbers of events predicted by the PWA fit for the D+ and P+ waves and their phase difference ∆Φ(D+ − P+) are shown as a function of M(ηπ ). There are eight ambiguous solutions in the fit [24,28,29], each of which leads to the same angular distribution. We show the range of fitted values for these ambiguous solutions in the vertical rectangular bar at each mass bin, and the maximum extent of their errors is shown as the error bar. The a2(1320) is clearly observed in the D+ partial wave (Fig. 3a). A broad peak is seen in the P+ wave at about 1.4 GeV/c (Fig. 3b). ∆Φ(D+ − P+) increases through the a2(1320) region, and then decreases above about 1.5 GeV/c (Fig. 3c). The intensities for the waves of negative reflectivity (not shown) are generally small and are all consistent with zero above about 1.3 GeV/c. These results are quite consistent with the VES results [12]. In particular, the shape of the phase difference is virtually identical to that reported by VES. (The magnitude of the phase difference is shifted by about 20 relative to that of VES.) Consistency checks and tests of the data have been carried out to determine whether the observation of the structure in the P+ wave could be an artifact due to assumptions made in the analysis or to acceptance problems. These include: fitting the data in restricted ranges of the decay angle; inclusion of higher angular momentum states; fitting the data with various t cuts; fitting the data using different parametrizations of the background; making cuts on other kinematic variables such as the πp or the ηp effective masses; and fitting data using events with η → πππ decays (with rather different acceptance from the 2γ events). The results are very stable and, in particular, the behavior of ∆Φ(D+ − P+) does not change in 6 any of these checks. Fits were also carri

A partial wave analysis of the ππ system produced in the charge exchange reaction: πp → ππn at an incident momentum of 18.3 GeV/c is presented as a function of ππ invariant mass, mπ0π0 , and momentum transfer squared, |t|, from the incident π − to the outgoing ππ system. For small values of |t|, the S-wave intensity shows a broad enhancement at low mπ0π0 with a sharp dip in the vicinity of the f0 (980). A dip is also observed in the vicinity of the f0 (1500). There is rapid variation of the S to D0 relative phase difference in these mass regions. For large values of |t|, the f0 (980) appears as a bump. The f2 (1270),

Results are presented on a partial wave analysis of the omega eta final state produced in pi (-)p interactions at 18 GeV/e where omega --> pi (+)pi (-)pi (0), pi (0) --> 2 gamma, and eta --> 2 gamma. We observe the previously unreported decay mode omega (1650) --> omega eta and a new 1(+-) meson state h(1)(1595) with a mass M = 1594(+/-15)((+10)(-60)) MeV/c(2) and a width Gamma = 384(+/-60)((+70)(-100)) MeV/c(2). The h(1)(1595) state exhibits resonant-like phase motion relative to the omega (1650). (C) 2001 Elsevier Science B.V. All rights reserved.

New measurements of peripheral meson production are presented. The data confirm the existence of exotic mesons at 1.4 and 1.6 GeV/c2. The latter state dominates the eta'pi- decay spectrum. The data on eta pi+pi-pi- decay show large strength in several exotic (Jpc = 1- +) waves as well.

The number of pseudoscalar mesons in the mass range from 1400 to 1500 MeV/c2 has been a subject of considerable interest for many years, with several experiments having presented evidence for two closely spaced states. A new measurement of the reaction π−p→K+K−π0n has been made at a beam energy of 18 GeV. A partial wave analysis of the K+K−π0 system shows evidence for three pseudoscalar resonances, η(1295), η(1416), and η(1485), as well as two axial vectors, f1(1285), and f1(1420). Their observed masses, widths and decay properties are reported. No signal was observed for C(1480), an IGJPC=1+1−− state previously reported in φπ0 decay.

The parameter α = −0.005 ± 0.007 (stat) ± 0.004 (syst) describing the density Preprint submitted to Elsevier Preprint 7 February 2008 of events within the η → 3π Dalitz plot has been measured using data from Brookhaven experiment E852. The result is compared to previous values and theoretical predictions.

In this paper we describe modifications to a previous theory for the altimeter electromagnetic bias (EM bias) of Srokosz [1986]. A major correction introduces a scaling of Srokosz's model by nonnegligible dimensionless ratios that depend on the slope variance of both long and short waves. With these modifications the EM bias is no longer simply a function of the cross skewness between surface elevation and slope but now depends on the variance ratios that represent the modulation between short and long waves, Inclusion of these ratios can reduce previous EM bias estimates by as much as 50%. Different directions for the longwave and shortwave field are also accounted for in the two-dimensional development of our approach. A radar frequency dependence consistent with observation is also predicted by the new model. Derivation extending our development to the next higher order in wave statistics is also presented and discussed.

A partial-wave analysis of 9082 hppn events produced in the reaction p2p→hp1p2n at 18.3 GeV/ c has been carried out using data from experiment 852 at Brookhaven National Laboratory. The data are dominated byJ50 partial waves consistent with observation of the h(1295) and theh(1440). The mass and width of theh(1295) were determined to be 1282 65 MeV and 66 13 MeV, respectively, while the h(1440) was observed with a mass of 1404 66 MeV and a width of 80 621 MeV. Other partial waves of importance include the 1 11 and the 1 waves. Results of the partial wave analysis are combined with results of other experiments to estimate f 1(1285) branching fractions. These values are considerably different from current values determined without the aid of amplitude analyses.

The mass and width of the a0(980) have been independently determined from a nearly background free data sample and the coupling constants to the eta-pi and K-K-bar modes have been determined

Details of the analysis of thehp system studied in the reaction p2p→hp2p at 18 GeV/c are given. Separate analyses for the 2 g andppp decay modes of the h are presented. An amplitude analysis of the data indicates the presence of interference between the a2 (1320) and aJ51 wave between 1.2 and 1.6 GeV/c. The phase difference between these waves shows a phase motion not attributable solely to the a2 (1320). The data can be fitted by interference between the a2 (1320) and an exotic 1 21 resonance with M5(1370616230 ) MeV/c and G5(3856402105 165 ) MeV/c. Our results are compared with those of other experiments.@S0556-2821 ~99!06119-6#

A cylindrical multiwire drift chamber with axial charge-division has been constructed and used in experiment E852 at Brookhaven National Laboratory. It serves as a trigger element and as a tracking device for recoil protons in π p interactions. We describe the chamber's design considerations, details of its construction, electronics, and performance characteristics.

The $\eta \pi^{-}$ system has been studied in the reaction $\pi^{-} p \to \eta \pi^{-} p$ at 18 GeV/c. A large asymmetry in the angular distribution is observed indicating interference between L-even and L-odd partial waves. The $a_{2}(1320)$ is observed in the $J^{PC}$ = $2^{++}$ wave, as is a broad enhancement between 1.2 and 1.6 GeV/c^{2} in the $J^{PC} = 1^{-+}$ wave. The observed phase difference between these waves shows that there is phase motion in addition to that due to $a_{2}(1320)$ decay. The data can be fitted by interference between the $a_{2}(1320)$ and an exotic $1^{-+}$ resonance with $M = (1370 \pm 16 {+50}\atop{-30}$) MeV/c^2 and $\Gamma =(385 \pm 40 {+65}\atop{-105}$) MeV/c^2.

A 3045 element lead glass calorimeter and an associated fast trigger processor have been constructed, tested and implemented in BNL experiment E852 in conjunction with the multi-particle spectrometer (MPS). Approximately, 109 all-neutral and neutral plus charged triggers were recorded with this apparatus during data runs in 1994 and 1995. This paper reports on the construction, testing and performance of this lead glass calorimeter and the associated trigger processor.

This paper reviews some of the important steps necessary to interpret multiscale atmospheric phenomena in SAR imagery, using examples from ERS-1. In some cases, it may be practical, with a combination of SAR imagery and conventional meteorological analysis, to effectively specify the MABL, including its depth and stability, surface wind speed and direction, and sea-surface stress or friction velocity, all on spatial scales down to a km or less. Such an application of SAR would represent a significant advance over conventional scatterometry, with typical spatial resolution of >20 km. This resolution is insufficient to resolve the turbulence structures in the MABL, and therefore also insufficient to deduce the surface wind corrected for atmospheric stability.

The recent search for non q q̅ mesons in π^-p interactions at Brookhaven National Laboratory is summarized. Many final states such as ηπ, η' π^-, a_0π, f_1π, a_2π, b_1π, which are favored decay modes of exotics, are under investigation.

The design, construction, and performance of a 198-element CsI detector built for Brookhaven experiment E852 is described. Design considerations for the array included such factors as rate, magnetic field, sensitivity and acceptance. Signals were obtained with a photodiode/preamplifier combination using PIN photodiodes. Data were taken over the course of two runs during the summers of 1993 and 1994. A calibration procedure using halo muons is described. The gain, energy resolution, and position resolution of the detector are discussed. Finally, the ability of the detector to be used as a low energy photon veto is illustrated using the data.

A scintillation detector meeting specific physics requirements and geometrical constraints is described. It operates with high efficiency inside a 1 T magnet in an intense charged particle beam of up to 3 × 106 particles/s. It uses a unique light collection system combining air space, wavelength shifter disc and conventional lucite light guides. The detector is used in a veto mode to identify interactions that produce an all-neutral final state. The details of the counter's design, construction and performance are described.