HPS Update John Jaros HPS Collaboration Meeting at JLAB May 22, 2018

What HPS has been doing since last time… Readying the 2015 Bump Hunt for publication Finalizing the 2015 Vertex Search Preparing the 2016 Data for Analysis Upgrading the SVT and Positron Trigger Planning the HPS Run in 2019 Targeting new physics for HPS Considering HPS Beyond 2019 HPS Update

Readying the 2015 Bump Hunt for Publication “And what rough beast, its hour come round at last/ Slouches towards Newport News to be born?” Omar showed first public HPS results at JLAB one year ago. Getting to final results required… * Rerunning analysis with TwPass6 * Evaluating Systematics * Completing an Analysis Note * Drafting the first HPS physics publication HPS Update

Evaluating and Correcting Systematics Mollers Scale Mass Resolution New Corrections Applied * Mass corrections due ztarget = -5 mm * A’ Radiative Tail (thanks Sebouh) Sources of Systematic Error * Mass Resolution different in data/MC * Radiative Fraction * Small biases in the Fits Results Composition Uncertainty Pulls vs Mass HPS Update

Analysis Note Omar et al. distributed the 2015 Bump Hunt analysis note on 12/18/2017 One complication: the new limit is worse than the old one. Why? Can we fix? HPS Update

Problems with the Fits Omar traced the discrepancy to two effects * Corrections in relating limits in 2 to limits from the fit due to A’ radiative tail and new estimates of sample composition (~30%) * New fits give substantially larger limits (x 2.5) Omar, Tim, and Matt G addressed problems with the fits * New result uses TwP6, which has worse mass resolution than P4. Worse resolution  wider mass bins  larger background uncertainty * Fix: New parameterization of background gives better fits with fewer parameters, so reduces background uncertainty * Bug in RooFit identified which made bias look artificially large. Switched to Minuit. Upper limits now under control. See Omar’s talk tomorrow for current status. HPS Update

Preparing a Draft Paper Writing Committee was formed, drafted the bump hunt paper, and distributed it on 03.03.2018. Comments were solicited. Comments have been addressed (thanks all who helped!) A new draft is ready to incorporate the final results when they are ready. HPS is very close to submitting its first physics result. HPS Update

HPS Experiment Overview Revisiting Procedures https://confluence.slac.stanford.edu/display/hpsg/HPS+Executive+Committee Live and learn. Some changes to present policy. See confluence for the full story. Analysis Note and New Results * Analysis Note is prerequisite for presenting any new HPS physics results * New results must be shown to HPS ≥ 1 week before public presentation * New results need EC, PPC, and at least 2/3rds of those voting for approval Presenting Thesis Results * Thesis results are public, so must adhere to rules above. * Results to be included in a thesis must be presented to HPS for comment at least 1 week prior to a student’s defense . HPS Experiment Overview

Finalizing the 2015 Vertexing Result Vertexing problems were identified in Pass6, required Pass7. * Covariance matrix for displaced vertices wrong (fixed by Matt, Miriam) Other fixes and fixers needed for Pass7 * SVT Flags set (thanks, Sebouh) * ECal steering files updated for calibration (…Holly) * Target z position (…Norman) * Ecal alignment revisited (…Nathan) * Ecal time corrections (…Holly) * Add beam spot and beam size Before After HPS Experiment Overview

Reconstruction and Re-Reconstruction Pass7 incorporated these fixes (thanks Norman and Rafo) * Lots of shepherding and organization needed * Big job: ~20k files, 7-15 hours/file * DB resource issues addressed * Timeouts and fatal exceptions dealt with Pass8 (thanks again Rafo) * SVT alignment constants from compact.xml * Re-processed all 0.5 mm 2015 data by mid-January * Re-processed all 1.5 mm 2015 data by mid March, which required new detector definition and SVT good flag (Norman, Sebouh) Vertexing problems solved. Just starting to discover Pass8 “features”. Will we eventually need Pass9? * Continuing puzzles: target position, track-Ecal match, T/B Asym… * Do we know beam spot position, beam angles,…? Completed, but wrong SVT alignment constants were used, so… See talks from Norman, Miriam, and Bradley HPS Experiment Overview

Vertex Progress with Pass8 Holly’s L1L1 Analysis with Pass8 looks promising * Mass vs decay length OK. Minimal high z background events. * Vertex errors fixed, so V0 projection to target gives better discrimination. Old New eliminates more bkg events HPS Experiment Overview

Vertex Progress with Pass8 Matt S shows some L2L2 backgrounds originate from trident production in L1 dead silicon! Vertexing Studies require more and better MC * Generated tritrig-wab-beam with full 2015 statistics at SLAC (Takashi, Jeremy) * Add MC truth to ntuple (Matt S) * Add beam tilt and profiles (Bradley) * Simulate beam backgrounds more accurately (Bradley) y ≥ 0.5mm z ~ zL1 pe+e ~ pbeam Vertex y [mm] Events Vertex z [mm] Pe+e- [GeV/c] HPS Experiment Overview

New MC for Vertex Analysis Large MC Sample enables studies of zcut fits (Holly) Large MC Sample will help diagnose L1L1, L1L2, and L2L2 backgrounds (Matt) MC data Coulomb Scatters? HPS Update

Finalizing the 2015 Vertex Search Lots to hear about on Wednesday: HPS Update

Preparing for 2016 Data Analysis Sebouh’s thesis has provided a first look at 10% of 2016 Pass1 Data looks OK Performance similar to 2015 Limits are roughly as expected HPS Update

Preparing for 2016 Data Analysis https://confluence.slac.stanford.edu/display/hpsg/PhysRun2016+Pass2+Checklist Finishing touches needed for Pass2 See Alessandra’s talk HPS Update

Upgrading HPS The Upgrades are needed to secure HPS Vertex Reach in 2019 Positron Trigger Upgrade: Hodoscope * Boosts acceptance * Reduces WAB rate * Improves trident yield SVT Upgrade: L0 * Doubles z resolution * Boosts acceptance in z * Huge impact on reach HPS Update

Status of HPS Upgrades Rafo and Tim have updated EC on designs, progress, and schedule Positron Trigger Upgrade on track for completion Summer 2018 * Design reviewed and complete * Scintillator, wavelength shifter fibers, cables, FADCs in hand * PMTs purchased * Prototype tests in EEL SVT Upgrade planned completion Jan 2019 * Silicon sensors due Summer 2018 * Mechanical designs ready for review * Hybrid design reviewed and completed, in layout * SVT DAQ Update underway to incorporate RCE improvements Present status in talks by Rafo and Tim after lunch HPS Update

HPS Run in 2019 “Don’t look back. Something might be gaining on you.” A+ Physics! The HPS 2019 Run will explore virgin A’ parameter space, well-motivated by models of light, thermal dark matter. If 2m > mA’ > m , then A’  SM visibles. HPS Works! * Bump hunt is publication quality * Vertex resolution well-simulated * L1L1 backgrounds are minimal Rejection 107 : 1 HPS can see something new! Next Step: 4 PAC weeks at ~4.5 GeV * 8 week run Summer 2019 HPS Update

HPS Run in 2019 Don’t delay! Competition is coming. LHCb * Already reported A’µ+µ- searches * More coming from 2017-18 runs * Covers HPS territory in Run 3 (2021-2023) with trigger-less readout SeaQuest and CERN * SeaQuest will report soon on its 2017 A’µ+µ- test run * With proposed Ecal trigger, SeaQuest covers much of HPS territory (2019?) * CERN is entering the fray. New proposals (FASER, SHIP, NA62) are under consideration. HPS Update

CERN is Paying Attention https://indico.cern.ch/event/714087/timetable/ https://indico.cern.ch/event/644287/ New Proposals: SHIP, METHUSLA, FASER, milliQan, Codex-b Reports coming end of 2018, may be of interest HPS Update

New Physics Targets for HPS Already on the list * SIMPs (Matt S on Thursday) * True Muonium (Bradley on Thursday) * Dark pions and multi-lepton decays Translating A’ Limits to searches for other hidden vectors * Searches for dark photons provide constraints on other vector mediators which couple to B-L, B and L, etc. Ilten, Soreq, MW, Xue [1801.04847] A General, Data Driven Vertex Search? * Prerequisite: high efficiency, multi-particle tracking; recoil e- detection. * Signatures Single high impact parameter track, not pointing to material (miss a track) *Neutral two particle vertex, but include lower ESUM, wider angles Doubly charged two particle vertex (miss some tracks) *Multi-track vertices * Anything unexpected in our data? We should look! HPS Update

HPS 2019 and Beyond Many analysis possibilities! New Students and Post Docs Needed! * 2015 0.5 + 1.5mm Bump and Vertex * 2016 Bump Hunt * 2016 SIMP Search Many Service Opportunities! Ditto! * Continue to improve and refine tracking * Data storage, processing, and MC generation for a huge data set * Can we be ready to process and analyze 2019 data immediately? We may need to be if there is competition. Getting Ready for the 2019 Run will be the centerpiece of the next HPS Collaboration Meeting. Stepan will discuss running beyond 2019 on Thursday. HPS Update

Conclusions HPS is very close to a major milestone: Publishing the 2015 Bump Hunt Result 2015 Pass8 Recon, which incorporates many improvements, is letting us finalize the 2015 Vertex Search and ready it for publication. Sebouh’s first look at 2016 data looks promising. With a final alignment, we are ready to proceed with 2016 Pass2 and more physics analyses. SVT and Positron Trigger Upgrades will guarantee significant reach in 2019. We need them in time for the run. The 2019 run promises exciting physics, lots of data, and lots of analysis opportunities. More students and postdocs needed! We must publish the results from the remaining 2015 running and from 2016 in timely fashion. HPS Update