The main focus of the heavy flavor program at RHIC is to investigate the properties of the Quark-Gluon Plasma by studying its effect on open heavy flavor and quarkonia production. J/ψ suppression induced by Debye screening of the static Quantum Chromo Dynamics (QCD) poten- tial between c ¯ c pairs was originally hailed as an unam- biguous signature of Quark-Gluon Plasma (QGP) forma- tion [1]. However, this simple picture is complicated by competing effects that either reduce the yield, such as co-mover absorption [2, 3], or enhance it, such as in re- combination models [4–6]. Recently, a growing interest in studying the Υ meson and its excited states has been kindled as it is expected that color screening will be the dominant effect contributing to any observed suppression of bottomonium production in heavy-ion collisions. A full spectroscopy of quarkonia states is now clearly recognized as one of the key measurements needed to understand the matter produced in high-energy heavy-ion collisions [7]. In particular, it has been recognized that data on the particle spectra of bottomonia can provide valuable in- formation to constrain QGP models [8]. Due to the low production cross section of b - ¯ b at RHIC ( σ$_{b}$$_{-}$ ¯ b ≈ 1.9 µ b, [9]), recombination effects in A + A collisions are neg- ligible. At the same time, the interaction cross section of bottomonium with the abundantly produced hadrons in these collisions is small [10], so suppression due to absorption by hadronic co-movers is expected by these models to be relatively unimportant. However, it will still be important to study Υ production in d +Au colli- sions since available measurements by E772 [11] of cold nuclear matter effects on Υ production at lower energy show some suppression. Nevertheless, the amount of sup- pression seen for the Υ family is measured to be smaller than for charmonia. Therefore, bottomonium is expected to be a cleaner probe of high-temperature color screening effects. 

In addition to its important role in establishing decon- finement, a measurement of the Υ 1S, 2S, and 3S states in p + p and heavy-ion collisions can help to set limits on the medium temperature. The quarkonium measure- ments help in reaching these key goals because ( i ) an observation of suppression of Υ production in heavy-ions relative to p + p would be a strong argument in support of Debye screening and therefore of deconfinement [12], and ( ii ) the sequential suppression pattern of the ex- cited states is sensitive to the temperature reached in the medium [7]. In this regard, lattice QCD studies have seen a burst of activity in recent years. Studies of quarkonia spectral functions and potential models based on lattice 

## I. INTRODUCTION 

QCD indicate that while the Υ(3S) melts even before the deconfinement transition and the Υ(2S) is likely to $_{melt at RHIC (}$√$_{s}$$_{= 200 GeV), the Υ(1S) is expected}$ to survive [7, 13, 14]. Recent results [12, 15] indicate further that almost all quarkonia states ( J/ψ , ψ $^{′}$, χ$_{c}$ , χ$_{b}$ , Υ(2S)) melt below 1.3 T$_{c}$ and the only one to sur- vive to higher temperature is the Υ(1S), which melts at 2 T$_{c}$ , where T$_{c}$ ≈ 175 MeV is the critical temperature for the parton-hadron phase transition. Therefore, a sys- tematic study of all quarkonia states in p + p , d +Au, and Au+Au collisions will provide a clearer understanding of the properties of the Quark-Gluon Plasma. 

Suppression of the Υ(2S) and Υ(3S) should be measur- able at RHIC energies with increased integrated luminos- ity. In the near future, the larger luminosities proposed by the RHIC II program [16] will allow for a statistically significant measurement of all 3 states. With the ob- jective of embarking in such a long program, one of the first steps is to establish a baseline cross section measure- ment of the bottomonia states in p + p collisions. There are no previous measurements of Υ production in p + p at the top RHIC energy for heavy ions (an upper limit was estimated in the 2004 data with only half of the calorimeter [17]). The luminosities available at RHIC in the 2006 run provided the first opportunity to mea- sure bottomonium at the previously unexplored center- of-mass energy of √$_{s}$ = 200 GeV. A dedicated trigger algorithm exploiting the capabilities of the STAR electro- magnetic calorimeter is essential for this measurement, and its development in STAR allows the Υ family to be studied in the e $^{+}$e − decay channel. In this paper, we report our result for the Υ(1S+2S+3S) cross section at midrapidity, obtained with the STAR detector in p + p collisions at √$_{s}$ = 200 GeV via the e $^{+}$e − decay channel. This measurement uses an integrated luminosity of 7.9 pb − 1 collected during RHIC Run VI (2006). We com- pare our data to perturbative QCD calculations done at next-to-leading order (NLO pQCD) in the Color Evapo- ration Model (CEM) [16] and in the Color Singlet Model (CSM) [18]. 

The article is organized as follows. Section II explains the detector setup. The details of the quarkonia triggers are explained in Sec. III. The acceptance and trigger efficiency are discussed in Sec. IV. After a detailed dis- cussion of the data analysis procedure in Section V, we present our results and compare with pQCD calculations and with available data in Sec. VI. Our findings are sum- marized in Sec. VII. 

The main detectors used in the STAR quarkonia pro- gram are the Time Projection Chamber (TPC) [19], the Barrel Electromagnetic Calorimeter (BEMC) [20], and 

## II. DETECTOR OVERVIEW 

