EF04 Topical Group Conversation

US/Eastern
Description

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Meeting ID: 955 4136 9778

Password: 120464

Rajan Gupta
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probing scalar and tensor interactions
lattice QCD calculation of ME and direct searches

lattice: calculate nucleon charges to probe new interactions
can look at same reaction at LHC (d->u+e+nu)

measurement in (ultra)cold neutron decay sensitive to new physics
parameterize with Fierz interference term, energy-dependent part of correlation between neutrino and anti-neutrino spin and momentum

relate terms above to BSM couplings

current uncertainties on charges are ~50%
goal: reduce to 10%; plot with impact of this reduction
should be able to do this with 300/fb at LHC?
low-energy measurements needed to be competitive (need 1e-4 level; now we are at 1e-3 level? big challenge for nuclear physics community)

Emanuele Mereghetti
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continuing Rajan slides
most sensitive processes: DY
issue: contributions at dim-8
need to include those terms to cross section, not done so far

1e-4 level nuclear measurement: need to control SM contributions at that level
experimental component

feedback
experimentalists at LHC on top of these analyses, expect that to continue
nuclear part: improve technology to measure suppressed terms in cross section; improve EFT calculations

Ayres: mentioned DY dim-8: not clear if LHC collaborations intend to include them; should we ask them to do this, or can use publish unfolded data?
EM: so far using published data; could be added to analysis if experimentalists convinced

Junping: how can helicity suppressed interactions be separated?
EM: look at angular distributions of leptons in DY, look at A0 and A4: scalar and vector-vector interactions give different distributions

Vladimir Livtinenko
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looking at using energy-recovery LINACs
high-energy Higgs production (ttH, ZHH)
proposal: develop lattice and simulations to explore physics in 500-600GeV c.o.m. energy

big question: how important is beam polarization in e+e- collider with c.o.m. in 90-600GeV range?
FCC-ee will not have; CLIC and ILC will, at higher energies

Ayres: there is no important physics target in which polarization is a must; it makes some measurements more efficient
at the end it is tradeoff: with polarization you may lose luminosity, but improve efficiency, and the two balance

e.g., H production from W fusion (only left-handed W used)

Jakob Beyer: mentioning 90GeV; at Z pole, polarization does give qualitative difference, can do different measurements; this seen to be relevant in comparison between 
CLIC and LEP
Ayres: could do with AFB?

Tania Roberts: 500-600GeV: would probably look at TDR of CLIC and ILC, many studies of polarized beams
https://arxiv.org/abs/2012.11267
Ayres: there is a 15-yr old report on polarization
https://arxiv.org/abs/hep-ph/0507011

Junping: role of polarization could be different if there is new physics present; would help probing nature of new physics

Junmou Chen
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2->3 VBS and Higgs self-coupling measurements

look at VLVL->VLVLH and VLVL->HHH

focus on c6 operators, w/ one, three or no propagator
w/ 3 operators: have two scales appearing at high energy, one from SM, one from BSM coupling
BSM and SM amplitudes scale (roughly) like squared ratio of scales: in high-energy limit, BSM becomes dominant

note non particularly strong enhancement in VV->VVH compared to VV->HHH

full simulation, problem and solution
  transverse polarization dominates cross section -> select longitudinal polarization only for final states
  enhancement of cross section of VV->VVH partly cancelled by log enhancement of SM cross section -> make pT cuts

some results from simulation: cross section vs energy
general conclusion: cross sections generally increase with c.o.m., but remain small until 5TeV -> this makes them useful only for high-energy muon collider?

looked also at pp->jjWWH
similar results, cross sections not very large at 14TeV, but sizable at 100TeV; in general, smaller cross sections and smaller enhancement than in ee case

HHH case: cross section smaller than WWH, but larger enhancement with energy

bottom line: 2->3 VBS excellent channel for Higgs self-coupling study, but only at high energy
amplitudes increase with square of energy
can look at 5-point scalar vertices from c6 operators
similar behavior of cross section in pp machine

feedback from community: no particular need now, probably when finishing project

Junping: for simulation: would like to request any MC from Snowmass MC TF?
JC: probably, will look into them

Gianfranco Morello
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mu-RWELL technology
micro-resistive WELL is a micro-pattern gaseous detector
compact, simple, with intrinsic spark protection (resistive layer from GEM used to quench sparks)

resistive layer harms rate capability -> different charge evacuation schemes

low-rate version: single resistive layer (SRL_
use 500-600V, holes in active are work as ionization chambers
limitation in area: depends on distance from the center of layer

high-rate versions: DRL (double layer) and SG (silver grid)
DLR: use two layers, with matrix of vias to connect them (1cm^2); hard to produce industrially; a 3D charge evacuation scheme

SG: 2D evacuation, easier to produce industrially

prototypes built and tested (at PSI)
rate capability: 5-10MHz/cm^2 (actually, could be higher? spot at beam line was not covering full area?)
gain: up to 1e4
space resolution <100um
efficiency: 98%

proponing to install low-rate version in CePC/FCC-ee IDEA (preshower and muon detector)
test beam at CERN H8 NA

building narrow prototypes, 50cm long (the IDEA layers will be 50x50cm^2)

competition between TPC and mu-RWELL for SCT apparatus (CREMLIN)

low-rate application for neutron detections: different cathode geometry or addition of Boron
GEANT4 simulations on going

high-rate application for LHCb muon station at HL-LHC
would need about 600 detectors -> need interaction with industry

Sam Lane
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EW restoration at LHC: VH channel

goal: look at HZ process and compare to HG: test Goldstone boson equivalence

parton level results: cross section longitudinally dominated
(look at VH helicity dependence)

look at SM VH cross section and EW-restored GH cross section

simulation, cut on DNN output to separate S and B
use MG5/PYTHIA/DELPHES
plots of pT(H)

signal strength in 1-lepton case
strength uncertainty (of all channels combined) 40% LHC and 6% at HE-LHC

chi2 vs pT(H) troubles: statistical uncertainty at high pT hides problems
looking at KL divergence, as better estimator: shows that the two hypotheses are in agreement

Ayres: what would you say if LHC measurement indicated deviations?
SL: would interpret as breakdown of EW symmetry at that energy
Ayres: sharp question: there is physics BSM, would this prove that NP is due to different ways of EW breaking?
Ian Lewis: started thinking about this

Junping: at higher pT, statistical uncertainty higher... which part of spectrum dominates contribution?
SL: first bin has indeed big effect
Junping: does this mean not helpful to go to high energy?

Samuel Homiller
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SMEFT fits (https://arxiv.org/abs/2007.01296 https://arxiv.org/abs/2102.02823)

SMEFT: playing more and more relevant role, as we do not see clear signals of NP

updated global fit in 2007.01296
new: full NLO QCD corrections in SMEFT for VH and VV
leading log NLO corrections

NLO effects do matter: they affect bins that give the most constraining power
effect of QCD corrections and anomalous couplings do not commute: important to use full predictions of SMEFT

strategy:
integrate out new particles at matching scale (few TeV)
generate subset of SMEFT coefficiencts
evolve coefficients down to EW scale (numerical changes can have significant effect on limits; new operators may also appear)
fit to H, diboson, EWPO data at EW scale and set limits on physical parameters

walked through procedure for a few models in recent paper

new work w/ goal: understand numerical importance of 1-loop matching effects (in singlet-model)
tree-level results
see that 1-loop can change by ~10% effect of tree-level result, except when large values of portal coupling

list of open questions:
- understand linear vs quadratic approximations
- compare effect of dim-8
- include top data
- include complete 1-loop matching to other models, more NLO...

Junping: there is EF04 group doing global fit

Richard Ruiz
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physics simulation at multi-TeV muon collider

big question: why mu collider now
mu collider probe muon flavor itself, beside business of energy and cleanliness
novel R&D shows that O(10TeV) muon collider are feasible
context of EF04: partonic collisions at Q~O(10TeV) we look at when electroweak symmetry is nearly restored (mW,mZ/Q->0)

details of MadGraph developments relevant to mu collider

looked at VBS and VBF vs s-channel
multi-TeV mu collider can be seen as vector boson collider
sigma(VBF) becomes more relevant than s-channel mu+mu- above 3-5TeV
same trend in the case of multi-boson production
done systematic study, this behavior seems universal

new: effective vector boson approximation (EVA)
should come out in a couple of months
idea is to consider W and Z, at high Q, as partons, and treat them as gluons in QCD: W/Z PDF to be released soon in MG5

complication in polarization to be addressed/discussed, but still putting this in MG5
VV production example
importance of longitudinal vs transverse depends on number of H
bottom line: now polarized scattering amplitudes can be done with MG5

Alessandro Tricoli: approach of W/Z PDF: what interplay/advantage with respect to calculating (with resummation) the V scattering?
RR: advantages: numerical stability (avoid large logarithms), anticipating availability of fully-resummed EW PDF, now sort of fool-proofing MG5
unclear to what extent accuracies of un-resummed EW PDF, resummed ones, and partial ME calculations compare with full ME calculation (terms, for example, from DGLAP 
evolution...)
this is subtle aspect being investigated

Veena Balakrishnan
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VBS scattering
looking at dim-8 operators
focus on 3, 6, and 10TeV samples; would then look at 30TeV

final states: WWZG
not possible to separate s-channel and VBS

look for BSM signal, with interference and quadratic term added to SM signal
cross sections have non-trivial sqrt(s) dependence, some complication with MC generation

look at dilepton mass in simulation

another state: WWWW
used MG5, 5k events
calculated SM, interference, and quadratic terms to cross section; compared their addition (after separate calculation) and the complete calculation with all terms: match 
at high energy, not so much in 3TeV case?

questions:
- which c.o.m. energies to consider
- leptonic vs hadronic modes
- VBS vs s-channel?
- effect of detector acceptance on sensitivity
- want to check cross sections with WHIZARD

Ayres: about energies: we have official table
Alessandro Tricoli: shall post (3,10,14,25,30 for muon, and some benchmarks for luminosity; slide 19 in 
https://indico.fnal.gov/event/44870/contributions/198445/attachments/135764/168821/EFintro_CPM_Oct2020.pdf)
Richard Ruiz: question about fiducial cuts for muon collider detectors: will we have "official" set?
Ayres: eta acceptance probably smaller than ILC detector (10deg from beam)
John Stupak: there is a baseline DELPHES card for muon collider MC (https://github.com/delphes/delphes/blob/master/cards/delphes_card_MuonColliderDet.tcl)

Tania Roberts: there was a discussion last week about integrated luminosity
Alessandro Tricoli: table discussed with accelerator people as well
seems that agreement about energy is ok, unclear luminosity?
issue of discussion: luminosity declared for 30TeV is not realistic (in Alessandro's link)
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    • 1
      Open discussion
      Speakers: Adam Martin (University of Notre Dame), Andre de Gouvea (Northwestern University), Aram Apyan (Fermi National Accelerator Laboratory), Brigitte Vachon (McGill University), Cen Zhang (Institute of High Energy Physics, Chinese Academy Sciences), Daniel Britzger, Daniel Stolarski, Daniel Wiegand (Northwestern University/Argonne National Lab), Emanuele Mereghetti (Los Alamos National Laboratory), Gianfranco Morello (INFN-LNF), Graham Wilson (University of Kansas), Ian Lewis (University of Kansas), Jakob Beyer (DESY), Jeffrey Berryhill (Fermilab), Jenny List (DESY), Jiayin Gu (JGU Mainz), John Michael Roney (University of Victoria), Juan Alcaraz Maestre (CIEMAT - Madrid), Junmou Chen, K Yumino, Keping Xie (University of Pittsburgh), Li Huang, Maximilian Swiatlowski (TRIUMF), Mogens Dam (Niels Bohr Institute, Copenhagen University), Paolo Azzurri, Radja Boughezal (Argonne National Laboratory), Rajan Gupta (Los Alamos National Lab), Richard Ruiz (Universite catholique de Louvain), Roberto Petti (University of South Carolina), Samuel Homiller (Harvard), Samuel Lane, Saptaparna Bhattacharya (Northwestern University), Sergei Chekanov (ANL), Siqi Yang, Sven Heinemeyer (IFT (CSIC, Madrid)), Swagato Banerjee (University of Louisville), Taikan Suehara (Kyushu University), Takahiro Mizuno, Veena Balakrishnan, Vladimir Litvinenko (Stonybrook University), William Shepherd (Sam Houston State University), Yang Ma (University of Pittsburgh), Yongcheng Wu (ycwu@physics.carleton.ca), bo li