Searching for Highly Ionising Parccles at the LHC

The MoEDAL Experiment – Searching for Highly Ionising Par>cles at the LHC

MoEDAL

Vasiliki A. Mitsou

October 23 – 25, 2017, Santander, Spain

Interna>onal collabora>on

~70 physicists from

~20 par>cipa>ng ins>tu>ons

UNIVERSITY OF ALABAMA UNIVERSITY OF ALBERTA

INFN & UNIVERSITY OF BOLOGNA UNIVERSITY OF BRITISH COLUMBIA CERN

UNIVERSITY OF CINCINNATI CONCORDIA UNIVERSITY

GANGNEUNG-WONJU NATIONAL UNIVERSITY UNIVERSITÉ DE GENÈVE

UNIVERSITY OF HELSINKI IMPERIAL COLLEGE LONDON KING'S COLLEGE LONDON KONKUK UNIVERSITY UNIVERSITY OF MÜNSTER

MOSCOW INSTITUTE OF PHYSICS AND TECHNOLOGY NORTHEASTERN UNIVERSITY

TECHNICAL UNIVERSITY IN PRAGUE QUEEN MARY UNIVERSITY OF LONDON INSTITUTE FOR SPACE SCIENCES, ROMANIA STAR INSTITUTE, SIMON LANGTON SCHOOL TUFT'S UNIVERSITY

IFIC VALENCIA

Point 8

MoEDAL at LHC

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Monopole & Exo>cs Detector At LHC

velocity: β = v/c

Key feature: high ionisa>on

charge

High ionisa_on (HI) possible when:

▫  mul_ple electric charge (H⁺⁺, Q-balls, etc.) = n × e

▫  very low velocity & electric charge, i.e. Stable Massive Charged Par_cles (SMCPs)

▫  magne_c charge (monopoles, dyons) = ng_D = n × 68.5 × e

!  a singly charged rela_vis_c monopole has ionisa_on ~4700 _mes MIP!!

▫  any combina_on of the above

= z/β

Par>cles must be massive, long-lived & highly ionising to be detected at MoEDAL

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Electric charge

Bethe-Bloch formula

Magne>c charge

Ahlen formula

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MoEDAL detectors have a threshold of z/β ~ 5 – 10

MoEDAL sensi_vity

Cross-sec_on limits for magne_c and electric charge assuming that:

▫  ~ one MoEDAL event is required for discovery and ~100 events in the other LHC detectors

▫  integrated luminosi_es correspond to about two years of 14 TeV run

De Roeck, Katre, Mermod, Milstead, Sloan, EPJC72 (2012) 1985 [arXiv:1112.2999]

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MoEDAL offers robustness against _ming and well-es_mated signal efficiency

MoEDAL physics programme

Highly ionising par_cles

Magne_c monopoles

KK extra dimensions

D-maqer

Quirks Q-balls

Black-hole remnants Doubly

charged Higgs

SUSY R-hadrons

sleptons

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MoEDAL physics program Int. J. Mod. Phys. A29 (2014)

1430050 [arXiv:1405.7662]

Searching for massive, long-lived &

highly ionising

par>cles

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MoEDAL detector

MoEDAL is unlike any other LHC experiment:

▫  mostly passive detectors; no trigger; no readout

▫  the largest deployment of passive Nuclear Track Detectors (NTDs) at an accelerator

▫  the 1^st _me trapping detectors are deployed as a detector

DETECTOR SYSTEMS

①  Low-threshold NTD (LT-NTD) array

•  z/β > ~5 – 10

②  Very High Charge Catcher NTD (HCC-NTD) array

•  z/β > ~50

③  TimePix radia_on background

monitor

④  Monopole Trapping detector (MMT) MoEDAL

LHCb

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1 ️ ⃣ & 2 ️ ⃣ HI par_cle detec_on in NTDs

•  Passage of a highly ionising par_cle through the plas_c NTD marked by an invisible damage zone (“latent track”) along the trajectory

•  The damage zone is revealed as a cone-shaped etch-pit when the plas_c sheet is chemically etched

•  Plas_c sheets are later scanned to detect etch-pits

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Looking for aligned etch pits in mul_ple sheets

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1 ️ ⃣ & 2 ️ ⃣ NTDs deployment

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2012: LT-NTD

NTDs sheets kept in boxes mounted onto LHCb VELO cavern walls

2015-2016: LT-NTD Top of VELO cover Closest possible loca_on to IP

2015-2016: HCC-NTD

Installed in LHCb acceptance between RICH1 and TT

3 ️ ⃣ TimePix radia_on monitor

•  Timepix (MediPix) chips used to measure online the radia_on field and monitor spalla_on product

background

•  Essen_ally act as liqle electronic “bubble-chambers”

•  The only ac_ve element in MoEDAL

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•  256×256 pixel solid state detector

•  14×14 mm ac_ve area

•  amplifier + comparator + counter + _mer

2015 deployment of MediPix chips in MoEDAL

Sample calibrated frame in MoEDAL TPX04

4 ️ ⃣ MMT: Magne_c Monopole Trapper

•  Binding energy of monopoles in nuclei with finite magne_c dipole moments of O (100 keV)

•  MMTs analysed with superconduc_ng quantum interference device (SQUID)

•  Material: Aluminium

▫  large nuclear dipole moment

▫  rela_vely cheap

•  Persistent current: difference between resul_ng current a•er and before

▫  first subtract current measurement for empty holder

▫  if other than zero → monopole signature

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Typical sample &

pseudo-monopole curves

MMTs deployment

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2012

11 boxes each containing 18 Al rods of

60 cm length and 2.54 cm diameter (160 kg)

2015-2016

•  Installed in addi_onal loca_ons: sides A & C, too

•  Approximately 800 kg of Al

•  Total 2400 aluminum bars

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•  @ 8 TeV JHEP 1608 (2016) 067 [arXiv:1604.06645]

•  @ 13 TeV Phys.Rev.Leq. 118 (2017) 061801 [arXiv:1611.06817]

Magne_c monopoles

•  Mo_va_on

▫  symmetrisa_on of Maxwell’s eqs.

▫  electric charge quan_sa_on

•  Proper_es

▫  magne_c charge = ng = n×68.5e coupling constant = g/Ћc ~34

▫  spin and mass not predicted

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MoEDAL improves reach of monopole searches w.r.t. cross sec_on & charge

Drell Yan mechanism Photon fusion

HIGHLY IONISING

Produc>on mechanisms in colliders

Box diagram

MMT2015: scanning

•  Analysed with SQUID at ETH Zürich

•  Excellent charge resolu_on (< 0.1 g

) except for outliers

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No monopole with charge > 0.5 g

observed in MMT samples at 99.5% CL

Persistent current after first passage for all samples

Detector: prototype of 222 kg of aluminium bars

Exposure: 0.371 a^-1 of 13 TeV pp collisions during 2015

PRL 118 (2017) 061801 [arXiv:1611.06817]

Persistent current for multiple measurements of candidates

Geometry

Material descrip_on between IP & detector

Kinema_cs

Event genera_on of Drell Yan produc_on

coupling ⪼ 1 ⇒ non-perturba_ve!

Propaga_on in maqer

• Ahlen formula

• Monopole energy loss

• Stopping range

MMT2015: analysis

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JHEP 1608 (2016) 067 arXiv:1606.01220

[rad]

1.6 1.8 2 2.2 2.4 2.6 2.8 3

[GeV]ZkinE

0 200 400 600 800 1000 1200 1400 1600 1800 2000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 MoEDALSimulation

DY spin-1/2, m = 1000 GeV

MMT2015: results

•  First monopole searches at 13 TeV at LHC

•  First limits for magne_c charge of 5 g

and masses > 3.5 TeV

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Detector: prototype of 222 kg of aluminium bars

Exposure: 0.371 a^-1 of 13 TeV pp collisions during 2015

PRL 118 (2017) 061801 [arXiv:1611.06817]

DY spin-1/2 DY spin-0

Monopole mass limits

•  Mass limits are highly model-dependent

▫  Drell-Yan produc_on does not take into account non-

perturba_ve nature of the large monopole-photon coupling

•  Exclude low masses for

|g| = 4g_D for the first _me at LHC

•  World-best collider limits for

|g| ≥ 2 g_D

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DY lower mass limits

[GeV] |g| = g_D |g| = 2g_D |g| = 3g_D |g| = 4g_D MoEDAL

13 TeV

spin ½ 890 1250 1260 1100

spin 0 460 760 800 650

MoEDAL 8 TeV

spin ½ 700 920 840 —

spin 0 420 600 560 —

ATLAS 8 TeV

spin ½ 1340 — — —

spin 0 1050 — — —

PRL 118 (2017) 061801 [arXiv:1611.06817]

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•  What about electrically-charged par_cles?

Why MoEDAL when searching for long-lived charged par_cles?

•  Trigger

▫  ATLAS and CMS must use trigger ➪ decreased signal efficiency

▫  MoEDAL has no trigger

•  Event selec>on

▫  ATLAS/CMS apply strict kinema_c cuts to suppress backgrounds

▫  complex analyses requiring elaborate systema_cs es_ma_on (and correla_ons)

▫  in MoEDAL analyses are hardware oriented ➪ simple and robust

▫  MoEDAL mostly limited by geometrical acceptance and low-β requirement

•  Timing: signal from (slow-moving) SMCP should arrive within the correct bunch crossings for ATLAS/CMS

▫  MoEDAL is _me-agnos_c ➪ no problem with very slow par_cles

•  When looking for trapped par>cles

▫  monitoring of detector volumes in an underground/basement laboratory has less background than using empty butches in LHC cavern

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SUSY long-lived par_cles (relevant for MoEDAL)

•  Long-lived sleptons (staus mostly)

▫  Gauge-mediated symmetry-breaking (GMSB):

stau NLSP decays via gravita_onal interac_on to gravi_no LSP

▫  Coannihila>on region in CMSSM: long lived stau, when m(τ̃) − m(χ̃₁⁰) < m(τ)

➜ naturally long life_me for stau in both cases

•  R-hadrons

▫  Gluinos in Split Supersymmetry: g̃qq̄, g̃qqq, g̃g

!  long-lived because squarks very heavy

!  gluino hadrons may flip charge as they pass through maqer

▫  Stops: t̃q̄, t̃qq

!  e.g. stop NLSP in gravi_no dark maqer

!  e.g. as LSP in R-parity viola_ng SUSY, long-lived when RPV coupling(s) small

•  Long-lived charginos

▫  Anomaly-mediated symmetry-breaking (AMSB): χ̃₁^± and χ̃₁⁰ are mass degenerate ⇒ χ̃₁^± becomes long-lived

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τ ! → τ χ !

t ! → t G !

χ !

→ π

χ !

SUSY long-lived par_cles (relevant for MoEDAL)

•  Long-lived sleptons (staus mostly)

▫  Gauge-mediated symmetry-breaking (GMSB):

stau NLSP decays via gravita_onal interac_on to gravi_no LSP

▫  Coannihila>on region in CMSSM: long lived stau, when m(τ̃) − m(χ̃₁⁰) < m(τ)

➜ naturally long life_me for stau in both cases

•  R-hadrons

▫  Gluinos in Split Supersymmetry: g̃qq̄, g̃qqq, g̃g

!  long-lived because squarks very heavy

!  gluino hadrons may flip charge as they pass through maqer

▫  Stops: t̃q̄, t̃qq

!  e.g. stop NLSP in gravi_no dark maqer

!  e.g. as LSP in R-parity viola_ng SUSY, long-lived when RPV coupling(s) small

•  Long-lived charginos

▫  Anomaly-mediated symmetry-breaking (AMSB): χ̃₁^± and χ̃₁⁰ are mass degenerate ⇒ χ̃₁^± becomes long-lived

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τ ! → τ χ !

t ! → t G !

χ !

→ π

χ !

Doubly-charged Higgs

•  Extended Higgs sector in BSM models:

SU

(2) × SU

(2) × U

(1) P-viola_ng model

•  Higgs triplet model with massive le•- handed neutrinos but not right-handed ones

•  Common feature: doubly charged Higgs bosons H

as parts of a Higgs triplet

•  Life_me

▫  depends on many parameters:

Yukawa h_ij (long if < 10^-8), H^±± mass, ...

▫  essen_ally there are no constraints on its life_me ➜ relevant for MoEDAL

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Chiang, Nomura, Tsumura,

Phys.Rev. D85 (2012) 095023 [arXiv:1202.2014]

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•  In some Large Extra Dimension models the forma_on of TeV Black Holes (BH) by high energy SM par_cle collisions is predicted

▫  BH average charge 4/3

▫  slowly moving (β ≲ 0.3)

•  Charged Hawking BH evaporate but not completely

➜ certain frac_on of final BH remnants carry mul>ple charges

➜ highly ionising, relevant to MoEDAL

Black-hole remnants

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BHR charges @ 14 TeV LHC [CHARYBDIS+PYTHIA]

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Hossenfelder, Koch, Bleicher, hep-ph/0507140

M M −

Spanish involvement in MoEDAL

•  IFIC Team responsibili_es

▫  monopole propaga_on & interac_on with maqer in Geant4 simula_on

▫  simula_on of monopole produc_on via photon fusion

▫  monopolium phenomenology

▫  sensi_vity on (meta-)stable electrically-charged par_cles ➪ SUSY & doubly-charged Higgs

•  Management posi_ons

▫  VAM: Chairperson of the Collabora_on Board

•  Group M&O funded by Generalitat Valenciana

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z [mm]

y [mm]

Magne_c monopole stopping posi_on p = 600 GeV

IFIC Valencia Team

▫  Seniors: J. Bernabeu, VAM (leader), C. García, R. Ruiz de Austri,

V. Vento, O. Vives

▫  Postdocs: J. Mamuzic, A. Santra

Epele, Fanchiotti, Garcia-Canal, VAM, Vento, EPJ Plus 127 (2012) 60

Monopolium produc_on

@ LHC, √s = 14 TeV

monopole mass [GeV]

σ [˜]

•  MoEDAL is searching for (meta)stable highly ionising par>cles

▫  least tested signals of New Physics

▫  predicted in variety of theore_cal models

▫  design opGmised for such searches

▫  combining various detector technologies

•  Results on monopole searches at 8 TeV & 13 TeV published

▫  no magne_c monopole detected

▫  bounds set significantly extend previous results at high charges!

•  Looking forward to many more results from Run-II and beyond

▫  for other monopole interpreta_ons

!  produc_on via photon fusion

!  spin 1 monopoles

▫  with NTDs

▫  for electrically-charged par_cles

Summary & outlook

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Project supported by a 2017 Leonardo Grant for Researchers and Cultural Creators, BBVA FoundaGon

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Analysis procedure

•  Electrically-charged par_cle: dE/dx ~ β^-2 ➔ slows down appreciably within NTD

➔ opening angle of etch-pit cone becomes smaller

•  Magne_c monopole: dE/dx ~ lnβ

▫  slow MM: slows down within an NTD stack ➔ its ionisa_on falls ➔ opening angle of the etch pits would become larger

▫  rela_vis_c MM: dE/dx essen_ally constant ➔ trail of equal diameter etch-pit pairs

•  The reduced etch rate is simply related to the restricted energy loss REL = (dE/dx)10nm from track

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depth:

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Dirac’s Monopole

•  Paul Dirac in 1931 hypothesized that the magne_c monopole exists

•  In his concep_on the monopole was the end of an infinitely long and infinitely thin solenoid

•  Dirac’s quan_sa_on condi_on:

•  Where g is the “magne_c charge” and α is the fine structure constant 1/137

•  This means that g = 68.5e (when n=1)!

•  The other way around: IF there is a magne_c monopole then charge is quan_sed:

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Dirac String

€

ge= c 2

"

# $ %

&

' n OR g= n

2α ^{e ( from}

4πeg

c = 2πn n=1,2, 3..)

€

e = c 2g

"

# $

%

&

' n

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Complementarity of MoEDAL & other LHC exps

•  Op_mised for singly electrically charged par_cles (z/β ~ 1)

•  LHC _ming/trigger restricts sensi_vity to (nearly) relaGvisGc par_cles (β ≈ 1)

•  Typically a largish sta_s_cal sample is needed to establish a signal

•  ATLAS & CMS cannot be calibrated for highly ionising objects

•  Magne_c charge detec_on via its trajectory in non-bend plane

→ calibra_on introduces large systema_cs

•  Designed to detect charged

par_cles, with effec_ve or actual z/β > 5

•  No trigger/electronics → slowly moving (β < ~0.5) par_cles are no problem

•  One candidate event should be enough to establish a signal (no SM bkg)

•  MoEDAL NTDs are calibrated using heavy ion beams

•  Magne_c-charge sensi_vity directly calibrated in a clear way

ATLAS+CMS MoEDAL

MoEDAL strengthens & expands the physics reach of LHC

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Nuclear Track Detectors coverage

•  High acceptance in central region η~0

▫  back-to-back pair produc_on means probability >~ 70% for at least one SMCP to hit NTD

•  For par_cles over z/β threshold, detec_on efficiency prac_cally 100%

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Credit: Daniel Felea

2015 NTDs