Using the Apparatus to Probe the -Box James Dowd The College of - PowerPoint PPT Presentation

Using the 𝑅 𝑥𝑓𝑏𝑙 Apparatus to Probe the 𝛿𝑎 -Box James Dowd The College of William & Mary (for the 𝑅 𝑥𝑓𝑏𝑙 Collaboration) Sept. 28-30, 2017 This work was supported in part by the National Science Foundation under Grant No. PHY-1405857.

Overview • Qweak experiment 𝑞 𝑓𝑞 scattering to measure the weak charge of the proton, 𝑅 𝑥 റ – Used elastic asymmetry of • For ̴2 weeks, Qweak received beam at higher energy (3.35 GeV) – Another experiment hall had priority • Opportunity to use the apparatus to make an ancillary measurement – Relevant to the main Qweak experiment – Stands on its own merit 𝑞 𝑊 correction to 𝑅 𝑋 ℜ𝑓□ 𝛿𝑎 • Goal: Constrain and validate theoretical predictions of 𝑓𝑞 scattering at 3.35 GeV റ – Using inelastic asymmetry of The Electroweak Box James Dowd 2 Sept. 28-30, 2017

RC Motivation 𝑞 • Qweak measured 𝑅 𝑋 – Must include Electroweak Radiative Corrections 𝑊 Gorchtein and Horowitz* showed ⧠ 𝛿𝑎 • – Larger than previously expected GHRM – Significant hadronic physics uncertainties – Energy dependence • Examined further by several groups – Gorchtein, Horowits, and Ramsey-Musolf – Sibirtsev, Blunden, Melnitchouk, and Thomas – Carlson and Rislow – Hall, Blunden, Melnitchouk, Thomas, and Young AJM • Could impact Qweak precision * Gorchtein and Horowitz. Phys. Rev. Lett. 102 , 091806 (2009) The Electroweak Box James Dowd 3 Sept. 28-30, 2017

Published Nucl.Instrum.Meth. A781 (2015) 105-133 The 𝑅 𝑥𝑓𝑏𝑙 Apparatus Beam Properties 𝐹 ′ ≈ 1.1 𝐻𝑓𝑊 𝐹 = 3.35 𝐻𝑓𝑊 Concrete Shield Hut 𝑋 = 2.23 𝐻𝑓𝑊 Quartz 𝑅 2 = 0.075 𝐻𝑓𝑊 𝑑 2 Τ Cerenkov Bars 𝐽 = 145 − 180 𝜈𝐵 𝑄 𝑐𝑓𝑏𝑛 = 89% Toroidal Spectrometer Polarized Electron Beam Target 34.4 𝑑𝑛 LH 2 Liquid Hydrogen Target Acceptance-Defining 𝑈 ≈ 20 𝐿 Collimator 3.0 𝑙𝑋 Cryopower The Electroweak Box James Dowd 4 Sept. 28-30, 2017

Published Nucl.Instrum.Meth. A781 (2015) 105-133 The 𝑅 𝑥𝑓𝑏𝑙 Apparatus Beam Properties 𝐹 ′ ≈ 1.1 𝐻𝑓𝑊 𝐹 = 3.35 𝐻𝑓𝑊 Concrete Shield Hut 𝑋 = 2.23 𝐻𝑓𝑊 Quartz 𝑅 2 = 0.075 𝐻𝑓𝑊 𝑑 2 Τ Cerenkov Bars 𝐽 = 145 − 180 𝜈𝐵 𝑄 𝑐𝑓𝑏𝑛 = 89% Toroidal Spectrometer Production Mode 𝜄 𝑄𝑝𝑚 = −19.1 ∘ Mixed Polarization Transverse Mode 𝜄 𝑄𝑝𝑚 = 92.2 ∘ Only Transverse Polarized Electron Beam Target 34.4 𝑑𝑛 LH 2 Liquid Hydrogen Target Acceptance-Defining 𝑈 ≈ 20 𝐿 Collimator 3.0 𝑙𝑋 Cryopower The Electroweak Box James Dowd 5 Sept. 28-30, 2017

Kinematics Where does the Qweak Inelastic measurement sit? 𝑋 = 2.23 𝐻𝑓𝑊 𝑅 2 = 0.075 𝐻𝑓𝑊 2 GHRM 𝑊 integral 3 Kinematic Regions contributing to ⧠ 𝛿𝑎 • • Region I – Christy-Bosted parameterization – Uses 𝛿𝛿 → 𝛿𝑎 rotated structure functions • Region II – VMD + Regge Parameterization • Region III – DIS region AJM * Hall, Blunden, Melnitchouk, Thomas, and Young. Phys.Lett. B753 (2016) 221-226 The Electroweak Box James Dowd 6 Sept. 28-30, 2017

Outline of Analysis Extract Longitudinal 𝒇 − PV Inelastic 𝒇𝒒 Measured Remove Pion Remove other Background Asymmetry backgrounds Asymmetries Asymmetry • Pure transverse runs • Asymmetry • Asymmetries & signal • Beam polarization angle fractions • Signal fraction • Elastic radiative tail • Al target windows • Concrete bunker ‘punch - through’ • Others The Electroweak Box James Dowd 7 Sept. 28-30, 2017

Characterization of Pion Background Large difference between 𝐹 & 𝐹′ • π - Čerenkov Detectors – Leads to large pion background e - • 4” lead wall placed in front of lowest Čerenkov Detector 3 2 4 – Ranges out most electrons ⊗ 1 5 Čerenkov Detector 7 – Leaves mostly pions π - 6 8 7 Pb • Sacrifice statistics to make a ‘Pion detector’ e - MD7 sees mostly pions The Electroweak Box James Dowd 8 Sept. 28-30, 2017

Characterization of Pion Background 𝐹 & 𝐹′ • Large difference between π - Čerenkov Detectors – Leads to large pion background e - • 4” lead wall placed in front of lowest Čerenkov Detector 3 2 4 – Ranges out most electrons ⊗ 1 5 Čerenkov Detector 7 – Leaves mostly pions π - 6 8 7 Pb • Sacrifice statistics to make a ‘Pion detector’ e - Main Detector 7 sees mostly pions The Electroweak Box James Dowd 9 Sept. 28-30, 2017

Pion Background Fraction 𝜌 − 𝑓 − • Use ADC pulse height spectrum to distinguish particle type – ~5 times more light Electrons deposit • Allow normalization of the simulations to float independently 4 simulations: 𝑓 − & 𝜌 − – Separate GEANT – Fit to ADC spectrum with a Minuit minimization • Integrate each scaled simulation to get total yields – ‘Yield’ - beam current normalized rate, weighted by pulse height 𝑗 , background fraction – 𝑍 𝜌 & 𝑍 𝑓 → 𝑔 𝜌 • Will not work for main detector 7 – 4” Pb wall installed in front – Made into an effective pion detector – Low electron count – MD 7 Impossible to fit • Pion yield fractions 𝑗≠7 = 0.097 ± 0.033 𝑔 – 𝜌 𝑗=7 = 0.81 ± 0.06 – 𝑔 𝜌 The Electroweak Box James Dowd 10 Sept. 28-30, 2017

Asymmetry Extraction 𝑴 cos 𝜄 𝑄𝑝𝑚 𝑼 sin 𝜄 𝑄𝑝𝑚 𝑗𝑘 𝑗𝑘 𝑘 𝑘 𝑗 sin 𝜚 𝑗 𝐵 𝑛𝑓𝑏𝑡 = 𝐵 𝑑𝑏𝑚𝑑 = 1 − 𝑔 𝑩 𝒇 + 𝑩 𝒇 𝜌 3 𝑗 𝑩 𝝆 𝑴 cos 𝜄 𝑄𝑝𝑚 𝑼 sin 𝜄 𝑄𝑝𝑚 𝑘 𝑘 2 4 𝜚 𝑗 sin 𝜚 𝑗 +𝑔 + 𝑩 𝝆 ‘Many - Worlds’ Monte 𝜌 ⊗ 1 5 2 Carlo Minimization 𝜓 2 = ∑ 𝐵 𝑛𝑓𝑏𝑡 𝑗𝑘 𝑗𝑘 − 𝐵 𝑑𝑏𝑚𝑑 6 8 7 • The 16 measured asymmetries are parameterized Results for 𝜄 𝑞𝑝𝑚 ≈ −19° – Longitudinal vs Transverse – Electron vs Pion • Coefficients are in terms of input parameters – 2 pion yield fractions (w/ & w/o wall) – 2 polarization angles • Results for 𝜄 𝑞𝑝𝑚 ≈ 92° 4 extracted raw asymmetry components 𝑴 𝑩 𝒇 −3.1 ± 0.6 ppm 𝑼 6.9 ± 1.5 ppm 𝑩 𝒇 𝑴 8.6 ± 2.4 ppm 𝑩 𝝆 𝑼 𝑩 𝝆 −19.7 ± 4.7 ppm Preliminary, not for quotation! The Electroweak Box James Dowd 11 Sept. 28-30, 2017

Asymmetry Extraction 𝑴 cos 𝜄 𝑄𝑝𝑚 𝑼 sin 𝜄 𝑄𝑝𝑚 𝑗𝑘 𝑗𝑘 𝑘 𝑘 𝑗 sin 𝜚 𝑗 𝐵 𝑛𝑓𝑏𝑡 = 𝐵 𝑑𝑏𝑚𝑑 = 1 − 𝑔 𝑩 𝒇 + 𝑩 𝒇 𝜌 3 𝑗 𝑩 𝝆 𝑴 cos 𝜄 𝑄𝑝𝑚 𝑼 sin 𝜄 𝑄𝑝𝑚 𝑘 𝑘 2 4 𝜚 𝑗 sin 𝜚 𝑗 +𝑔 + 𝑩 𝝆 ‘Many-Worlds’ Monte 𝜌 ⊗ 1 5 2 Carlo Minimization 𝜓 2 = ∑ 𝐵 𝑛𝑓𝑏𝑡 𝑗𝑘 𝑗𝑘 − 𝐵 𝑑𝑏𝑚𝑑 6 8 7 • The 16 measured asymmetries are parameterized Results for 𝜄 𝑞𝑝𝑚 ≈ −19° – Longitudinal vs Transverse – Electron vs Pion • Coefficients are in terms of input parameters – 2 pion yield fractions (w/ & w/o wall) – 2 polarization angles • Results for 𝜄 𝑞𝑝𝑚 ≈ 92° 4 extracted raw asymmetry components 𝑴 𝑩 𝒇 −3.1 ± 0.6 ppm 𝑼 6.9 ± 1.5 ppm 𝑩 𝒇 𝑴 8.6 ± 2.4 ppm 𝑩 𝝆 FREE! 𝑼 𝑩 𝝆 −19.7 ± 4.7 ppm Preliminary, not for quotation! The Electroweak Box James Dowd 12 Sept. 28-30, 2017

Preliminary Result * Hall, Blunden, Melnitchouk, Thomas, and Young. 𝑄ℎ𝑧𝑡. 𝑆𝑓𝑤. , 𝐸88(1): 013011, 2013. * Model Predictions Preliminary Result 𝑅 2 = 0.09 𝐻𝑓𝑊 2 𝑅 2 = 0.075 𝐻𝑓𝑊 2 𝑞 𝐵 𝑞ℎ𝑧𝑡 = −8.8 ± 0.9 𝑡𝑢𝑏𝑢 ± 1.3(𝑡𝑧𝑡𝑢) ppm 𝐵 𝑄𝑊 = −7.8 ± 0.6 ppm 𝑞 𝐵 𝑄𝑊 ≈ −7.8 ± 1.2 ppm The Electroweak Box James Dowd 13 Sept. 28-30, 2017

Measurement Uncertainty • Limited by statistical uncertainty – Only ~2 weeks of data • Pion background fraction – Largest systematic uncertainty – Demonstrates that we can separate 𝑓 − & 𝜌 − when not in counting mode • Systematic uncertainty dominated by – Pion background fraction – Asymmetry Separation The Electroweak Box James Dowd 14 Sept. 28-30, 2017

Future Experiment Wishlist • Data that spans kinematic integral – 𝐹 , 𝑋 , and 𝑅 2 – Ex: Tune MOLLER apparatus to access various inelastic kinematics • Dedicated pion detector – Cleaner pion separation • More Statistics! The Electroweak Box James Dowd 15 Sept. 28-30, 2017