LBNL Physics Division Research Progress Meetings

Walter Hopkins - Using Direct Stop Searches at ATLAS to Constrain the Parameter Space of Supersymmetric Models
2015-09-01 16:00 - 17:00 (America/Los_Angeles)
Abstract:

A summary of the search for direct stop production in the 0-lepton channel is presented using 20 TeV data collected with the ATLAS experiment at the LHC. One of the stop decay modes considered is a stop decay to a top and a neutral lightest supersymmetric particle (LSP) resulting in signature with four or more jets and large missing energy. No excess is observed above the background expectation and limits are set on the stop and LSP masses and are presented as a function of stop decay branching fraction, combining the results from the 0 and 1-lepton channels. Additionally, the results are interpreted to confine the much larger parameters space of a more general supersymmetric model. Finally, outlook for stop searches for the LHC Run 2 will also be discussed.

Benjamin Schmidt (KIT, Germany) "Background discrimination capabilities and recent results of the EDELWEISS-III direct dark matter search experiment"
2015-09-22 16:00 - 17:00 (America/Los_Angeles)
Abstract:
The EDELWEISS collaboration is operating a large set of 36 massive cryogenic Ge detectors for the direct detection of Weakly Interacting Massive Particles (WIMPs) in the underground laboratory of Modane, France (LSM). The twofold detector readout in ionization and phonons allows a discrimination between nuclear recoils from the scattering of neutrons or WIMPs and electron recoils from the scattering of γ- and β-particles. As part of the R&D for the current data taking in EDELWEISS-III a new data analysis framework has been developed and evaluated on a dedicated commissioning run. Results on the surface event rejection of the detectors with advanced electrode design (FID) from this data-set will be presented. WIMP search data taking has been ongoing since August 2014 and the latest results of a low mass WIMP analysis will be discussed.

Miland Diwan (Brookhaven National Laboratory), "Challenges and Opportunities for a Long Baseline Neutrino Experiment "
2015-09-24 16:00 - 17:00 UTC
Title: Challenges and Opportunities for a Long Baseline Neutrino Experiment
Abstract: Neutrino mass and mixing is one of the few indications of new physics beyond the standard model, and new theoretical and experimental work is needed to understand neutrino properties and their role in the Universe as the most abundant particle of matter. I will briefly review the current state of understanding of neutrinos properties. I will then describe the current optimization for the Fermilab based LBNF/DUNE program focusing on most important technical challenges.

Special RPM - Yifang Wang (IHEP, China) "CEPC-SPPC: an initiative in China for the future of HEP"
2015-09-25 10:30 - 11:30 UTC | INPA Common Room (50-5026), 50-5026
Abstract:
Since the discovery of Higgs, the future of HEP is a key question to the community. Needless to say, accelerator-based energy frontier of HEP is still playing the central role, and a right approach is vital for the health of our field. We proposed in 2012 the following plan for the next several decades: a circular e+e- collider as a Higgs factory for the precision test of SM and search for hints beyond the SM, followed by a ~ 100 TeV proton collider in the same tunnel for direct searches. This is also a natural continuation of Beijing Electron-Positron Collider(BEPC) which will end its operation around 2022. Since then a preliminary design report for the accelerator, detector and civil construction is completed. I will report the status, progress and efforts towards a CDR and establishment of the international collaboration.

Zack Slepian (Harvard University) "The Baryon-Dark Matter Relative Velocity and a New Approach to the 3-Point Correlation Function"
2015-09-29 16:00 - 17:00 UTC
“The Baryon-Dark Matter Relative Velocity and a New Approach to the 3-Point Correlation Function”
Due to their different behaviors before decoupling (z~1020), at high redshift (z~50) there is a relative velocity between baryons and dark matter that is coherent on very large scales. If this relative velocity couples to galaxies today, it can shift the BAO peak in the galaxy-galaxy 2-point correlation function. Such a shift would systematically bias the expansion history inferred using the BAO method. I will give a configuration space picture of the relative velocity and show that the 3-point correlation function can be used to remove this systematic bias from the BAO method. I will then present a reformulation of the 3PCF that:

permits computing the 3PCF in N^2 not N^3 time, N the number of objects
allows analytic calculation of a highly accurate covariance matrix
gives perturbation theory predictions in excellent agreement with both mock catalogs and data

Using this approach on ~700,000 galaxies in SDSS DR12 constrains linear and non-linear bias and demonstrates a ~2.5 sigma BAO feature in the 3PCF. I’ll conclude with prospects for using this approach, and an analogous one for the anisotropic 2PCF, on DESI.

Simon Fiorucci (Brown Univ.) "The latest on the LUX dark matter experiment: How it got there, and where it is going"
2015-10-08 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
LUX has set the standard for direct dark matter detection experiments since its result announcement in 2013. In order to get there, several years of science planning and incremental successes had to happen. Today LUX serves a dual purpose:
– It is still the leading, currently operating experiment in the field. I will detail the strategy toward new exciting results in the near (and even immediate) future. I will also highlight those critical advances which have allowed LUX to keep its edge.
– It is a testbed and an incubator for the next generation of dark matter experiments, and specifically LZ. Aside from training up the next generation of physicists, there are extensive plans before the end of the experiment in 2016 which promise to yield very valuable data on detector technology options, calibration techniques and validity of simulation models. I will go over these and how they fit into both LUX and LZ strategies.

Ken Heller (Univ. Minnesota) "NOνA Begins – First Results from the NOvA Neutrino Oscillation Experiment"
2015-10-29 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
The NOνA long baseline neutrino oscillation experiment has just completed its initial data run and the analysis of that data. This run constitutes about 8% of the planned data. The first run resulted in a measurement of the oscillation of muon neutrinos into two modes. One the disappearance of muon neutrinos, the 2-3 oscillation, and the other the appearance of electron neutrinos, the 1-3 oscillation. In addition to describing the results and their impact on the neutrino mass ordering and CP violation, I will describe the construction and design of this unique 14 kiloton detector.

Reserved (TBD)
2015-11-05 16:00 - 17:00 (America/Los_Angeles)

J. Duarte (Caltech) "Naturalness Confronts Nature: Searches for Superparticles at CMS"
2015-11-10 16:00 - 17:00 (America/Los_Angeles)

C.M. Delitzsch (U. of Geneva) "Jet substructure techniques at the LHC: a probe of physics beyond the Standard Model"
2015-11-12 16:00 - 17:00 (America/Los_Angeles)

Anna Patej (Harvard) "Distributions of Baryons from the Virial Radius of Galaxy Clusters to Large Scales"
2015-11-17 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
I will discuss my recent work on the distributions of baryonic matter on various scales, from the gas and galaxies in galaxy clusters to the clustering of massive galaxies on large scales. Near the virial radius of galaxy clusters, long-standing analytical models of structure formation as well as recent simulations predict the existence of steep density jumps in the gas and dark matter profiles. I will describe a new method for deriving models for the gas distribution in galaxy clusters, which relies on a few basic assumptions — including the existence of such density jumps — and show a resulting profile for the gas that is in good agreement with X-ray observations of cluster interiors and simulations of the outskirts.
Since cluster member galaxies are expected to follow similar collisionless dynamics as the dark matter, the galaxy density profile should show a steep density jump as well. I will address the question of whether we can find evidence for a feature consistent with a density jump with current observations, and will additionally discuss avenues for probing the density jumps with future data sets.
Moving to larger scales where massive galaxies of different types are expected to roughly trace the same large-scale structure, I will present a test of this prediction by measuring the clustering of red and blue galaxies at z~0.6 using the CMASS sample of galaxies from DR12 of SDSS-III. The stochasticity between these two samples can be quantified via the correlation coefficient r, which can be constructed from two different statistics, both of which indicate that on intermediate scales (20 < R < 100 Mpc/h) there is low stochasticity between the two samples of galaxies.
Lastly, I will describe some ongoing and future observational efforts, focusing on my involvement with the DECam Legacy Survey (DECaLS), a pathfinder imaging survey for the upcoming Dark Energy Spectroscopic Instrument (DESI) galaxy redshift survey.
Slides

Sara Simon (Princeton) "The Atacama B-Mode Search: Cosmic Microwave Background Polarimetry at 17,000 Feet"
2015-11-19 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
The Atacama B-mode Search (ABS) was a crossed-Dragone telescope located at an elevation of 5200 m in the Atacama Desert in Chile that observed the cosmic microwave background (CMB) from February 2012 until October 2014. ABS searched for the primordial B-mode polarization signal at large angular scales from multipole moments of l~40 to l~500, where it is expected to peak. The ABS focal plane consisted of 240 pixels sensitive to 145 GHz, each containing two transition-edge sensor bolometers coupled to orthogonal polarizations. Cold optics and a warm, rapidly rotating half-wave plate made the ABS instrument unique. I will discuss the ABS instrument and its contributions to the field of CMB cosmology.

Sheldon Stone (Syracuse Univ.) "Pentaquarks and Tetraquarks at LHCb"
2015-11-24 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
I will discuss the discovery of two pentaquark states both decaying into a J/ψ meson and a proton. The decay mode defines the quark content as c cbar, u, u, d, and thus are called charmonium pentaquarks. These exotic structures are found in Λb→J/ψ K- p decays whose existence and properties are determined from a full amplitude analysis using 7 and 8 TeV pp collision data corresponding to an integrated luminosity of 3/fb collected by the LHCb experiment. The two states will be shown to be of opposite parity and have spins 3/2 and 5/2. I will also present a determination of spin parity of the the Z(4430) tetraquark meson, also a charmonium state. Finally different models of pentaquark structure will be discussed.

Hongtao Yang (CERN) "ATLAS Measurement of Higgs Boson Production in the Diphoton Decay Channel and ATLAS-CMS Combined Measurement of the Higgs Boson Mass"
2015-12-03 16:00 - 17:00 (America/Los_Angeles)
Abstract:
Understanding the properties of the newly-discovered Higgs boson has been one of the priorities of the LHC physics program. In this talk, I will present the measurement of Higgs boson production processes in the diphoton decay channel using 4.5/fb of pp collisions at 7 TeV and 20.3/fb at 8 TeV collected by the ATLAS experiment at the LHC, and discuss the essential role of this decay channel in the Higgs boson coupling studies. I will also cover the measurement of Higgs boson mass based on the combined data samples of the ATLAS and CMS experiments in the high resolution diphoton and four-lepton decay channels.

Lene Bryngemark (Lund U.) " Searches for Physics Beyond the Standard Model Using Dijets in ATLAS"
2015-12-10 08:00 - 17:00 (America/Los_Angeles)
Abstract:
The LHC gives us access to the highest collider energies, at the highest intensities, providing a unique opportunity to thoroughly examine the constituents of matter and their interactions at ever smaller distances and higher mass scales. Jets are produced in the highest momentum transfer collisions and are thus at the energy frontier. With the recent increase in LHC beam energy, ATLAS makes use of this sensitivity to make its first statements of what physics looks like in a new energy regime. In this presentation, I show the results from both the 8 and the more recent 13 TeV analysis of dijet mass and angular distributions. I also mention some possible extensions of this analysis to further enhance its discovery potential for physics beyond the Standard Model.

Ben Nachman (SLAC) "Measuring and Exploiting the Quantum Properties of Jets with the ATLAS Detector"
2015-12-15 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Quarks and gluons hadronize before their properties can be directly measured. However, information about the origin, electric charge, and color charge of high energy quarks and gluons is embedded in the resulting collimated sprays of hadrons known as jets. This information defines the quantum properties of jets: the observable consequences of the quantum properties of quarks and gluons on the jets they form. Such properties are often subtle, but the ATLAS collaboration has recently demonstrated that even the electric and color charge can be extracted with high precision. These measurements have important implications for probing the emergent properties of the strong force at the highest available energies and for searching for physics beyond the Standard Model.

Special RPM - Rachel Mandelbaum (CMU) "Recent Progress and Future Prospects for Weak Lensing Cosmology""
2015-12-16 16:00 - 17:00 (America/Los_Angeles)
Abstract:
Measurements of weak gravitational lensing (coherent shape distortions of distant galaxies due to the lensing effect of mass between us and those galaxies) and are among the most promising ways to learn about the equation of state of dark energy, the theory of gravity on cosmological scales, and the connection between galaxies and the dark matter density field. In this talk, I will review the state of the field of weak lensing, including recent cosmological analysis and prospects with future surveys. I will then discuss some of the obstacles to robust weak lensing cosmology, such as the difficulty in estimating coherent galaxy shape distortions in real data, or in removing the effect of coherent galaxy shape alignments that arise due to (for example) large-scale tidal fields. After presenting recent progress on both of these sources of systematic uncertainty, I will conclude with future prospects for reducing them to below the statistical error and enabling robust cosmological constraints with future large surveys such as LSST, Euclid, and WFIRST.

Tomo Lazovich (Harvard) "One Higgs, Two Higgs, Old Higgs, New Higgs: the Higgs boson from discovery to new physics with the ATLAS experiment"
2016-01-12 16:00 - 17:00 UTC | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

The discovery of the Higgs in Run 1 of the LHC provided a more complete picture of the Standard Model and also gave particle physicists a new tool to use in the search for Beyond the Standard Model physics. With center of mass energy now at 13 TeV in LHC Run 2, we are poised to produce new resonances and probe higher energy scales. I will first discuss the challenging WW decay channel of the Higgs and how we went from discovery to the current best measurement of the Higgs cross section and observation of the vector boson fusion production mode. I will then discuss searches for new physics in both resonant and non-resonant production of two Higgs bosons in the 4b final state in Run 2, detailing the advantages and difficulties of using this final state to search for new physics over a wide range of masses.

Franz Elsner (UCL) "Parameter estimation in cosmology - The Planck likelihood"
2016-01-14 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
The inference of cosmological parameters requires the construction of a likelihood function that acts as an interface between theory and observational data. Using the CMB experiment Planck as a worked example, I provide an overview of the challenges associated with the analysis of high-resolution, state of the art experiments. In particular, I will discuss the approximations necessary to make an analysis feasible in practice, the role of nuisance parameters, and tests used to assess the robustness of the results. Reviewing the most important cosmological implications of Planck, I will conclude with an outlook of what we can expect to learn from future experiments.

Shawn Westerdale (PRINCETON) "Detecting Dark Matter with DarkSide-50"
2016-01-19 16:00 - 17:00 (America/Los_Angeles)
Abstract:
Dark matter constitutes 85% of the matter in the universe, yet despite its abundance, very little is known about it. One popular theory is that dark matter is made of Weakly Interacting Massive Particles, or WIMPs. Due to the low cross section for WIMP-nucleus interactions, the event rate of WIMPs in a detector is expected to be very low. This means that detectors must have extraordinarily low background rates and good background rejection in order to be able to detect these rare events above their background.
DarkSide-50 is a 50 kg liquid argon time project chamber, nested inside of a 30 tonne boron-loaded liquid scintillator neutron veto, which is inside a 1000 tonne water Cherenkov muon veto. Since neutrons can leave a signal identical to what is expected from WIMPs, neutrons are the most dangerous background to such an experiment. I will talk about the latest results from the DarkSide-50 detector, which recently published results from 120 days of running background free. This talk will also have a focus on the design and performance of the neutron veto system that enables the detector to remain free of neutron backgrounds by vetoing neutrons with > 99.2% efficiency.

Walter Pettus (YALE/WISCONSIN) "The DM-Ice Dark Matter Experiment"
2016-01-21 16:00 - 17:00 UTC | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
DM-Ice is a phased program towards the first direct detection search for dark matter in the Southern Hemisphere with a quarter ton scale NaI(Tl) crystal array. It will provide an understanding of the modulation signal reported by DAMA by running arrays at both Northern and Southern Hemisphere sites. A first generation experiment with 17-kg of active mass, DM-Ice17, was deployed in December 2010 at a depth of 2457 m under the ice at the geographic South Pole and has concluded its 3.5-yr primary physics run. An active R&D program is ongoing at the Boulby Underground Laboratory to investigate clean crystals and optimize detector components. A worldwide consortium of sodium iodide experiments is now preparing two 100-kg arrays to start data taking in 2016. I will report on the successes of the DM-Ice program and how the stage is set for definitively testing the DAMA signal anomaly.

Gaosong Li (Shanghai Jiao Tong University) - "Daya Bay Experiment"
2016-01-26 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
The Daya Bay Reactor Neutrino Experiment is designed to measure the neutrino mixing angle with unprecedented precision. The experiment utilizes multiple pairs of identical antineutrino detectors (ADs) at different baselines from three pairs of reactor cores to minimize systematic uncertainties. In 2012, Daya Bay made the first definitive measurement of a non-zero value for $theta_{13}$ using the first 55 days of data collected with six ADs by measuring the antineutrino rate deficit. With the final two ADs installed, Daya Bay resumed data taking in full 8-AD configuration in late 2012. More than 1 (0.15) million electron antineutrino candidates had been collected with the near (far) site detectors by the end of 2013, significantly improving the precision on . In addition to precision measurement of neutrino oscillation parameters, analyses exploring various other physics potential are carried out.
In this talk, I will focus on the calibration system. I will present calibration related works I have been working on to improve the detector absolute efficiency and neutrino oscillation analysis. I will also present the results on neutrino oscillation parameters from an independent analysis.

Frank Golf (UCSB) "Searching for New Physics with the Large Hadron Collider"
2016-02-04 16:00 - 17:00 UTC | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
After a two-year shutdown, the LHC restarted proton-proton collisions in 2015 with an increase in center-of-mass energy to 13 TeV. I describe some early results with data from the first year of running and plans for the significantly larger datasets that we expect to collect in the coming years.

Neal Dalal (Univ. Illinois at Urbana-Champaign) "Detecting Dark Matter Substructure Using ALMA"
2016-02-11 16:00 - 17:00 UTC | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
Dark matter halos surrounding galaxies are expected to contain copious substructure, in the form of gravitationally bound subhalos. Local Group observations suggest that our Galaxy has a deficit of substructure (the Missing Satellites Problem), possibly indicating new physics in the dark sector. I will describe how gravitational lensing may be used to measure the amount of dark substructure that exists in typical galaxy halos. In particular, I will explain how observations by the newly commissioned ALMA observatory of dusty galaxies from CMB surveys can probe halo substructure. I will show first results from our ALMA Cycle 2 observations, and argue that ALMA should be able to answer the Missing Satellites Problem in upcoming years.

Special RPM | Daniel Holz (U. Chicago) " Observation of Gravitational Waves from a Binary Black Hole Merger"
2016-02-18 08:00 - 17:00 (America/Los_Angeles)
We will provide an overview of LIGO’s first event. The signal is consistent with the merger of two black holes of ~30 Msun at a distance of ~400 Mpc. We will discuss some aspects of the detection, including parameter estimation, tests of general relativity, and astrophysical constraints.

Andreu Font-Ribera (LBNL) "Studying the Expansion of the Universe with Quasar Spectra"
2016-02-23 16:00 - 17:00 UTC | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
From 2009 to 2014, the Baryon Oscillation Spectroscopic Survey (BOSS) used the SDSS telescope to obtain spectra of 1.5 million galaxies to get very accurate measurements of the Baryon Acoustic Oscillations (BAO) scale at redshift z ~0.5. At the same time, BOSS observed over 184 000 high redshift quasars (z>2.15) with the goal of detecting the BAO feature in the clustering of the intergalactic medium, using a technique known as the Lyman alpha forest (LyaF).
In this talk I will overview several results from the LyaF working group in BOSS, including the measurement of BAO at z=2.4 both from the auto-correlation of the LyaF (Delubac et al. 2015), and from its cross-correlation with quasars (Font-Ribera et al. 2014). From the combination of these studies we are able to measure the expansion rate of the Universe 11 billion years ago with a 2% uncertainty.
In the near future, the Dark Energy Spectroscopic Instrument (DESI) will increase this data set by an order of magnitude. DESI will provide an exquisite measurement of the expansion over cosmic time, while at the same time addressing other interesting questions: the sum of the mass of the neutrino species, properties of dark matter particles, tests of general relativity and the shape of the primordial power spectrum of density fluctuations.

Heather Gray (CERN) " Chasing Beauty: Probing the Higgs Using B-Quarks
2016-02-25 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:
In the Standard Model, the Higgs has the highest probability to decay to b-quarks, yet this is one of the most challenging channels to observe at the LHC. I will explain the importance of measuring the coupling to the Higgs b-quarks, outline the ATLAS Run-1 H->bb analysis and review the current status of our knowledge of the coupling of the Higgs to b-quarks. I will also discuss how we might expect to observe the coupling of the Higgs to b-quarks during Run-2 of the LHC or in the future. Finally, I will discuss future measurements towards the Higgs self-coupling to explore the mechanism of electroweak symmetry breaking.

Mariarosaria D'Alfonso (CERN) "New Physics at LHC: Energy and Precision Frontiers"
2016-03-01 16:00 - 17:00 (America/Los_Angeles) | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract:

The evidence for the existence of dark matter in the universe is overwhelming; yet its exact nature, its mass(es) and coupling constants, are completely unknown. If kinematically accessible at colliders, these particles are expected to be produced directly or in the cascade of other new hypothetical particles. At the same time, the global fit to electroweak precision data impressively demonstrates the predictive power of Standard Model. Increasing the theoretical and experimental precision on electroweak observables may reveal inconsistencies between measurements and predictions due to the presence of new particles in the loop corrections. I will discuss a discovery physics program to take the full advantage of the ability of the LHC to probe the energy and the precision frontiers. I will highlight how improved scientific instruments with new possibilities will enable these searches.

Julien Guy (LPNHE) " The Prospects and Challenges of the Dark Energy Spectroscopic Instrument
2016-03-03 16:00 - 17:00 UTC | Zoom Talk, 50A-5132, Berkeley, ca, 94720
Abstract :
I will present the prospects of DESI for the measurement of Dark
Energy in light of a decade of efforts to unveil its nature, from the
discovery of cosmic acceleration with type Ia supernovae, to the most
recent results with supernovae and baryon acoustic oscillations (BAO).
DESI will map cosmic expansion up to redshifts of 3, anchoring
distances at low redshift to the era of past deceleration with an
order of magnitude gain in precision compared to current surveys.
DESI data will offer a stringent test of the standard model of
cosmology, with important possibilities for discovery.
The project, however, is not free from experimental challenges. I will
review the analysis efforts needed to extract the whole potential of
the BAO probe, from the optimization and calibration of the efficiency
of the redshift survey, to the characterization of the instrumental
noise in the Lyman-alpha forests.

Sho Uemura (Stanford) "The Heavy Photon Search Experiment at Jefferson Lab"
2016-03-08 16:00 - 17:00 (America/Los_Angeles)
Abstract:
The Heavy Photon Search (HPS) is a new experiment at Jefferson Lab searching for massive U(1) vector bosons (also known as heavy photons, dark photons, or A prime with a weak effective coupling to electric charge. The heavy photon is motivated as part of a hidden sector” model of dark matter, where it would mediate the self-interaction of dark matter and the interaction of dark and ordinary matter. HPS is sensitive to heavy photons of mass 10-500 MeV with coupling strength episilon squared of 1e-5 to 1e-10. The HPS experiment is designed to produce heavy photons in a process analoguous to bremsstrahlung using an electron beam on a fixed target, and detect decays to e+e pairs with two signatures (invariant mass resonance and displaced decay vertex). The detector is a compact, large-acceptance forward spectrometer comprising a silicon microstrip tracker for momentum measurement and vertexing and an electromagnetic calorimeter for triggering on e+e. Precise beamline controls, high-rate trigger and DAQ, and good time resolution are needed for a detector that comes within 0.5 mm of the beam and is sensitive down to 15 mrad from the beam plane, and must cope with the intense beam background in this environment. A low-mass tracker and clean track reconstruction are needed for the best sensitivity. This talk will describe the HPS experiment and its current status after test, commissioning, and engineering runs.
