9 and is limited only by luminosity. The triggered distribu- tions shown in Figs. 3–6 are dominated by the π 0 photon background. These background events are rejected in the offline analysis. trigger, tracking, and TPC-BEMC matching efficiencies, we obtain a combined efficiency of 13.2% for the Υ(1S). A similar procedure was applied to the Υ(2S) and Υ(3S) states, which have slightly higher efficiencies due to their larger masses. We calculated a weighted aver- age among the 3 states, including the branching ratio and the ratio of cross sections, in order to obtain an average efficiency to be applied to the measured yield of Υ(1S+2S+3S). For this we use the branching ratios compiled by the PDG [27], and cross section ratios from NLO pQCD calculations in the Color Evaporation Model (CEM). The calculation used a bottom quark mass of m$_{b}$ = 4 . 75 GeV /c $^{2}$, the PDFs used are MRST HO [28], the choice of scale is µ = m$_{T}$ , and the center-of-mass energy is √$_{s}$ = 200 GeV [16]. The branching ratios and cross sections we used for this purpose are shown in Ta- ble II. This procedure results in a combined acceptance, trigger efficiency, track finding efficiency, and TPC- BEMC matching efficiency of 14.3% for the averaged Υ(1S+2S+3S) combination, see the last row of Table I. We estimate the sensitivity of the efficiency to the values in Table II in two ways. ( i ) By varying the branching ra- tio values by their uncertainty, we find that the efficiency varies in the range 14.2–14.4%. ( ii ) Instead of using the numbers from Table II, we can use measured values of the ratios Υ(2S)/Υ(1S) and Υ(3S)/Υ(1S) from Ref. [29]. No further input is needed because the weighted average of the efficiency does not depend on the overall scale of the cross section: it cancels out when averaging. By varying these measured ratios within their uncertainty we obtain weighted efficiencies in the range 14.1–14.4%. Therefore, our results do not depend strongly on the values in Table II. In particular, the overall scale of the cross section from the NLO calculations has no direct impact on our results. Additional analysis cuts related to electron iden- tification are discussed in the following section. With thresholds of ≈ 4 GeV, the hadron rejection power of the BEMC towers at the energy relevant for Υ decay daughters is e/h ≈ 100. The main source of back- ground for the trigger comes from high- p$_{⊥}$ π $^{0}$’s decaying into two photons that deposit energy in the BEMC. The BEMC will therefore trigger on two high- p$_{⊥}$ π $^{0}$’s with a large opening angle. These events are typically from di- jets. Since these are also produced by large–momentum- transfer events with low cross section, the trigger rate is sufficiently small even in the presence of this back- ground, that the Υ trigger can sample all collision events During the offline analysis, we use a complete emula- tion of the trigger to obtain all candidate BEMC tower pairs for an event. We use the TPC to select charged tracks and require that they point close in η - ϕ to the posi- tion of the candidate clusters. The TPC also allows us to obtain improved electron kinematics compared to those derived from BEMC information available at the trigger level and to perform particle identification via specific ionization. The matching of TPC tracks to BEMC clus- ters is also useful for electron identification via the ratio E/p . Tracks are selected based on the number of TPC points found during the track pattern recognition and used in the fit to obtain the track kinematic parameters. The TPC tracks can have a maximum of up to 45 space points. We require that all tracks have at least 52% of their maximum possible points, and a minimum of 20 points. The first requirement guarantees we have no split tracks, and the second requirement sets a floor for those tracks which have a number of points smaller than 45 due to passing through inactive areas of the detector. We select tracks with p$_{⊥}$ > 0 . 2 GeV /c to reject most low momentum tracks in a first pass. We do not im- pose higher p$_{⊥}$ requirements in the track selection stage because we also require E/p matching with the BEMC, where E > 2 . 5 GeV, as discussed below. Tracks are also required to extrapolate back to a primary vertex found in the event. We find the combined TPC acceptance times tracking efficiency for detecting each Υ daughter to be ϵ$_{TPC}$ = 85%, and to be approximately independent of electron p$_{⊥}$ . Hence, the pairwise efficiency can be ob- tained by squaring the single particle efficiency. In order to guarantee that the analysis only uses tracks that could have fired the trigger, we impose a requirement that the tracks extrapolate close to the BEMC candi- date towers. The requirement used was for them to be within a circle of radius R < 0 . 04 in η - ϕ space of the L2 candidate clusters. We find that this cut has an ef- ficiency of ϵ$_{R}$ = 93% for a given Υ daughter electron, and has good background rejection power. This is il- lustrated in Fig. 8, which shows the R distribution for simulated Υ(1S) daughters as the line histogram. The R distribution from tracks passing basic quality cuts in the triggered events is shown as the solid circles. An important component of the analysis is the vertex- finding efficiency. We find that in contrast to minimum- bias p + p events, the Υ triggered events have a very high vertex-finding efficiency. The analysis benefits from the presence of the HT trigger, since these events are likely to have a high- p$_{⊥}$ track that facilitates the task of find- V. Υ ANALYSIS TABLE II: Branching fractions for Υ(nS) → e $^{+}$e − [27] and total cross sections at √$_{s}$ = 200 GeV from an NLO CEM model [16]. See text for details. Υ state B (%) σ (nb) Υ(1S) 2.38 ± 0.11 6.60 Υ(2S) 1.91 0.16 2.18 Υ(3S) 2.18 ± 0.21 1.32