Jamie Nagle (University of Colorado, Boulder)

Department of Energy sPHENIX Science Review

Jamie NagleUniversity of Colorado

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Responding to the Recommendations1. More clearly articulate improvements in physics understanding

with sPHENIX in the context of ongoing studies at RHIC and LHC

2. Explore heavy-flavor tagged jet capabilities

3. Explore improved Upsilon resolution and statistics

4. Investigate more complete simulations to better understand instrumental effects

5. Explore extended pseudorapidity coverage for calorimetry

6. Consider prospects for increasing data rate and triggering

7. Investigate alternate jet observables to enhance useful range of jet finding

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Question #6Consider prospects for increasing

data rate and triggering

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Data Rates Au+Au @ 200 GeVIn the original proposal, we conservatively assumed RHIC performance

for Au+Au as in Run-14 (with full stochastic cooling in place). This corresponds to an ~8 kHz min.bias interaction rate within |z|<10 cm.

In the original proposal, we used a Level-1 accept rate of 10 kHz as the baseline (a good match to the interaction rate).

We noted that a limitation at this rate was the re-use of the PHENIX strip-pixel layers in the sPHENIX tracker.

New tracking design (see Tony Frawley’s talk) no longer includes the strip-pixels for multiple reasons including rate

capability and thickness

Updates from RHIC C-AD

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As recommended, we asked the Collider-Accelerator Division for updated projections. No major funds for new investments in

accelerator performance assumed.

Factor of 2.5 improvement within z-vertex selection relative to Run-14.

Thus, we revisited new Level-1 and DAQ archive goal.

New Level-1 DAQ Specs

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15 kHz good match to sPHENIX DAQ Architecture and luminosities

Tested PHENIX pixels DCM2 readout at ~ 15 kHz

In nominal one-year Au+Au run, one can thus record 100 billion Au+Au

minimum bias events within |z|< 10cm

With Au+Au rare triggers for physics that can be measure just with the

calorimeters (i.e. wider z-vertex range), and can sample 0.6 trillion events.

Cost/benefit analysis for widening the silicon vertex z-coverage does not

warrant that change.

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Rarest Triggers in Au+Au @ 200 GeVFor some of the calorimeter-only measurements, triggering in Au+Au would be needed to sample the full 0.6 trillion events.

• Photons• Photon-jet correlations

Straightforward to trigger on high energy EMCal Photons above E > 10 GeV

• Inclusive jets• Dijets

Jet patch trigger with event-by-eventbaseline subtract works for jet E > 35 GeV.Capability designed into calorimeter FEEand trigger information available

sPHENIX GEANT-4

Simulation

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Data Rates p+p @200 GeVIn the original proposal, we conservatively assumed RHIC performance

for p+p @ 200 GeV as in Run-12.

Updated C-AD projections including the Electron Lens provide a significant luminosity increase. Much of that being realized in Run-15.

Run15 Peak and avg near

double Run12Avg lumi increases

with peak

Run 12Avg lumi levels off relative to

peak

As you will see in the physicsprojections plots,

this removes the p+p baseline as the statistics limiter.

Need to demonstrate the Level-1 triggers can sample

this luminosity without biasing physics. Unbiased

measurements in Au+Au require clean p+p/p+A comparison.

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Triggering in p+p and p+A @ 200 GeV

Jet trigger (EMCal + HCal) fully simulated in GEANT-4. Quark Jets and Gluon Jets sampled with very high efficiency for

ET> 10 GeV without strong bias.Comparison with bias from EMCal only trigger.

Rate, Rate, Rate

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Translates not just into extended reach, but more critically more differential measurements (see later slides).

Statistics also lead to reducing systematic uncertainties.

g

p0

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Question #5Explore extended pseudorapidity

coverage for calorimetry

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RHIC Kinematics Reminder

Forward Calorimetry

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Additional underlying event characterization and jet containment in A+A.

Not critical to sPHENIX physics program, pursuing separately.

As a first step, GEANT-4 simulation of instrumenting hadronic calorimetry in place

of the flux return end doors.

Very interesting p+p and p+A low-x physics, which are part of the fsPHENIX concept.

Strong RIKEN interest in forward HCal

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Question #1More clearly articulate improvements in

physics understanding with sPHENIX in the context of ongoing studies at

RHIC and LHC

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Emergent Phenomena

Discovery of QGP as perfect fluid was huge!

We know a lot about how QGP behaves,

but not so much about how it really works.

Discovery of High Tc Superconductors was huge!

However, we still do not know what really carries the charge.

Now it is critical to probe QGP (High Tc Superconductors) at different length scales to get full insight.

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Sensitivity, Statistics, Key Knobs• RHIC greater sensitivity in key channels from kinematics

• RHIC ability to engineer surface bias and parton type

• RHIC sensitivity to emergence of perfect fluidity where coupling is strongest near transition temperature

• Key knobs to get at this physics,and with clear connection tosPHENIX observables

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Jet Geometry EngineeringThorsten Renk has explored the ability to engineer the surface and

energy loss bias to gain more information. Works particularly well at RHIC due to steeply falling jet spectrum.

sPHENIX can measure these jets with no minimum pT selection and no online trigger bias.

Thus, one can explore the full range of engineered geometries. Systematic measurements enabled “tomography”

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Photon-Tagged Jets

“The steeper falling cross sections at RHIC energies lead not only to a narrower zJγ distribution in p+p collisions

but also to larger broadening end shift in the <zJg>. “

LHC RHIC

Dai, Vitev, Zhang, PRL 110 (2013) 14, 142001

g

q

g (E=20 GeV), S/B is 20x better at RHIC Underlying event 2.5x smaller

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Path Dependence

Equark

Ephoton

sPHENIX unique mapping of path (L) dependence of parton-QGP interactions.

Key to resolving strongest coupling near transition temperature and why.

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Different Medium, Different Jets

Can we observe the strongest coupling near Tc definitively

Inner workings? (quasiparticles, fields,

Sound modes)

How do the parton shower and medium

evolve together?

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Jet-Medium Interactions

Strongest coupling near Tc as Perfect Fluid Emerges

pQCD as running, are probes weakly

coupled at all scales?

Coup

ling

Stre

ngth

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Stronger Coupling Near Tc

“Jet Quenching is a few times stronger near Tc relative to the

QGP at T > Tc.”Liao and Shuryak, PRL (2009)

“The surprisingly transparent sQGP at the LHC [compared to RHIC]”

Horowitz and Gyulassy, NPA (2011)

“Large v2 is striking in that it exceeds expectations of pQCD

models even at 10 GeV/c.”PHENIX, PRL (2010)

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Detailed Path Dependence

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Upsilon MeltingsPHENIX combined with LHC measurements can

really pin down screening effects and temperature

dependence

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Parton virtuality evolves quickly and is influenced by the

medium at the scale it probes

Thick lines indicate where the QGP

influences virtuality evolution

RHIC Jet ProbesLHC Jet ProbesQGP Influence

Bare Color Charges

Thermal Mass Gluons

Perfect Fluid Only

Unique critical microscope resolution

at RHIC.

Measurement overlap between RHIC and LHC

very important too.

Jet Probes of QGP Structure

Virtuality Evolution

Rise in RAA at LHC is important – though

different models have different underlying

physics.

YAJEM rise results for virtuality evolution,

i.e. changing scale for resolving the

medium.

Key test at RHICand with precision

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Scale in the Medium

Limit of infinitely massive scattering centers yields all

radiative e-loss.

Medium parton

qhat scattering of leading parton radiation e-lossehat energy transferred to the QGP medium

q scattering of leading parton which then radiates

e energy transfer from parton to QGP particle

^

^

Importance of Beauty-tagged jets

at RHIC and LHC

Heavy b-masssuppresses radiation!

Collisional energy loss much more important

CollisionalRadiative

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Heavy Quark JetsBeauty Quark

Forward radiation suppressed, dead-cone.

Separating collisions versus radiative energy loss.

Key handle on what is being scattered from in medium

Jet Energy Distribution

Coleman-Smith et al. Vitev et al.

Additional sensitivity to contributions of radiative and collisional energy loss mechanisms

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New Interest in p+AsPHENIX provides discriminating power on p+A physics explanationsEnabled by p+p/p+A HCal triggering (as done in CMS for example)

sPHENIX covers up to very high Bjorken x2.

x2 ~ 0.06

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Current RHIC Capabilities, Why sPHENIX?PHENIX – high rate, deadtimeless DAQ, but very limited acceptance

STAR – large acceptance, modest rate, no HCal, limited Upsilon acceptance/separation

• Rate, Rate, Rate unbiased physics samples, differential observables• Critical triggering in p+p and p+A for full comparisons

Upsilon

Hadrons

Kinematic Reach

Photon Statistics

p+A

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Why sPHENIX with LHC?Kinematics give RHIC observables key sensitivity

Difference quark/gluon admixture

Probing critical dependencies in temperature, virtuality, scale

Enormous statistics without bias for fully differential analyses

Extension in energy, temperature, scale, etc. have proven in this field to provide

invaluable constraints on the underlying physics.

SummaryConnection from the QCD Lagrangian tophenomena of confinement and asymptotic freedom was fundamental

Connection from QCD to the emergent phenomena of near perfect fluidity of the Quark-Gluon Plasma near the phase transformation is just as fundamental

Pinning down h/s tells us the nature of the QGP,more importantly we need to reconcile:

Most important discovery in field: perfect fluid &

Crucial part of QCD: weak coupling at short distances

Without sPHENIX this critical scientific answer will be lost

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BACKUP MATERIAL

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Observables RoadmapQuestions Observables Needs

Are there relevant screening lengths in QGP

Is QGP Coupling Strongest near Tc?

At what length scale does the QGP go from strong to

weak coupling?

How do parton showers evolve in the QGP?

Are there quasiparticles in medium?

Are there significant medium response modes to high energy partons? Upsilon three state

suppression

Jet inclusive spectra

Dijet correlations

Jet fragmentation functions

Heavy flavor tagged jets

Jet – global event structure observables

g-jet/h correlations

Large AcceptanceHigh Rate

Electron IDPhoton ID

Full Calorimetric Coverage

A New Detector at RHIC

High data acquisition rate capability, 15 kHz

Sampling 0.6 trillion Au+Au interactions in one-yearMaximizing efficiency of RHIC running

BaBar Magnet 1.5 T

Coverage |h| < 1.1

All silicon trackingHeavy flavor tagging

ElectromagneticCalorimeter

Hadronic Calorimeter

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Forward CalorimetryThere is an LOI for an Electron Ion Collider Detector

built around the BaBar Magnet and sPHENIX Calorimetryhttp://arxiv.org/abs/1402.1209

There is also strong interest in forward sPHENIX,Including the hadron-going spectrometer from the above LOI.

http://www.phenix.bnl.gov/phenix/WWW/publish/dave/sPHENIX/pp_pA_whitepaper.pdf

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T3 [G

eV3 ]

Time [fm/c]

Differential measure is most sensitive to

coupling near Tc

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Beauty Jets and Radiation SuppressionSlide from Yen-Ji Lee (QM14)

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PRL 2011Guangyou Qin, Berndt Muller Larger modification

at RHIC,more of parton shower

equilibrated into medium.

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EE

EEAJ

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Quark-Gluon Kinematics

Photon-Tagged Jets also identify the

partner as a light quark jet.

Gluons are elusive, and yet very important with a much stronger color

coupling to the medium.

Triggering on a 20 GeV R=0.2 jet, has a very strong surface bias and selects out quark jets. Partner probability to be a gluon jet to the quark is ~ 65%. Excellent opportunity to compare quark and

gluon samples. Again, opportunity as a function of L.

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Over-constraining the Problem

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Direct Photon-Jet/h

In Au+Au central collisions for pT > 20 GeV, direct

photons dominate S/B > 3

Simple isolation cuts with full calorimetry give

additional handle and enable p+p and p+A

comparison measurements

sPHENIX has excellent direct photon capabilities

LHCRHIC

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RHIC dominated by “fake jets”? No.

arXiv:1203.1353Phys. Rev. C86 (2012) 024908

Simple Answer = Over Key Kinematic Ranges Jet Physics is accessible with sPHENIX

without requiring jet bias cuts

Multiple techniques being developed in the field to extract jet results. This is a demonstration of one such technique following the ATLAS method.

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Unique Measurement ExamplePredictions that Fragmentation Function D(z) = p / Eparton will have dramatic high-z suppression

If Ejet < Eparton in A+A due to out of cone radiation or medium excitation or … then shifting z denominator

sPHENIX enables precision measurement

Cannot be done otherwise at RHIC

Coupled with precision measure at LHC across

different jet energies and different QGP couplings Definitive Answers

arXiv:0710.3073

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RHIC and LHC Together

It is fundamental to making major (paradigm changing) advances in the field to probe the QGP (through different

temperature evolutions) at a range of length scales.

That program requires sPHENIX for precision overlapping and unique measurements from both RHIC and LHC

Kinematic differences also play a major role with sPHENIX changing the

data landscape and constraining the

underlying physics and QGP properties

LHC Physics in the Next Ten Years

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Run 2 Run 3

Pb+Pb Pb+Pb/p+Pb Pb+Pb/p+Pb/Ar+Ar

sPHENIX measurements well timed with LHC Run-3 measurements

Very good for enabling theory focus on simultaneous understanding

RHIC

LHC Higher Energy Jet Observations

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Large suppression of balanced dijets with pT,1 > 120 GeV/c

Fully calorimetric measurement, no low pT cutoff on constituents

Original expectation is huge suppression of high z Fragmentation

Functions. Not observed.

Correlated bias in which jets and how much of their energy is reconstructed.

Key check with g-jet/h

STAR Jet Program

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Very good jet capabilitiesLarge acceptance, tracking + EMCal

Exciting recent results from QM2014Trigger on jet > 20 GeV requiring online trigger of > 5.4 GeV in one EMCal tower and all pT > 2 GeV

Expect Surface Bias on TriggerAnd Long Path on Opposite Side

However, only modest suppression of balanced jets

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Now re-run jet algorithm with all particles around

originally found jets

Dijet asymmetry identical in pp and AA!

Very different result from theory expectations and LHC results.

If full jet energy recovered, real unbiased FF measurements available to sPHENIX.

Biased di-jet case may select particular geometry.

Perhaps biased towards both jets tangential.

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RHIC Jet Discriminating Power

http://arxiv.org/abs/arXiv:1207.6378

Major new detector project at RHICLarge coverage calorimetry coupled with high rates

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EE

EEAJ

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Near Transition Temperature Enhancement

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Single hadron v2Single hadron RAA

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RHIC with sPHENIX and STARsPHENIX DAQ bandwidth 15 kHz STAR DAQ bandwidth 2 kHzDeadtimeless DAQFull digitized calorimeter information for EMCal high tower and patch triggerLevel-1 triggered (full flexibility)

sPHENIX A+A can record 100B and sample 600B Full out MB currently, STAR would record 10B

HCal enables full jet patch trigger in p+p, p+A Utilizes EMCal trigger in p+p, p+A and A+AHCal enables fragmentation function measure with p and E independent HCal enables charged hadron triggeringHCal enables good photon isolation cuts Utilizes EmCal and Tracks HCal rejects electron backgrounds Electron ID with TPC, TOF, EMCalHCal acts as magnetic flux returnHCal in detector with tracking – both ATLAS/ Only STAR/ALICE jet typesCMS jets and STAR/ALICE jets for comparisonUpsilon large acceptance and mass resolution STAR MTD 1/7 of acceptance, lower resolution

•sPHENIX huge data sample with jets with very good statistics in the energy range 20-70 GeV, includes key overlap with LHC jet range and methods•HCal resolution best in upper range, sPHENIX uniquely enables FF measurement, enables to dial the surface engineering bias to do full tomography