Jets in the standard model and beyond the standard model Gavin Salam CERN, Princeton & LPTHE/CNRS (Paris) PANIC, MIT, 28 July 2011 Parton fragmentation Gluon emission: dE dθ quark αs ≫ 1 Z E θ At low scales: αs → 1 Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 2 / 25 Parton fragmentation Gluon emission: dE dθ quark αs ≫ 1 Z E θ θ At low scales: gluon αs → 1 Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 2 / 25 Parton fragmentation Gluon emission: dE dθ quark αs ≫ 1 Z E θ At low scales: αs → 1 Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 2 / 25 Parton fragmentation Gluon emission: dE dθ quark αs ≫ 1 Z E θ At low scales: αs → 1 hadronisation non−perturbative Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 2 / 25 Parton fragmentation Gluon emission: π+ dE dθ quark αs ≫ 1 Z E θ KL π0 At low scales: K+ − αs → 1 hadronisation π non−perturbative Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 2 / 25 Parton fragmentation Gluon emission: π+ dE dθ quark αs ≫ 1 Z E θ KL π0 At low scales: K+ − αs → 1 hadronisation π non−perturbative This is a jet Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 2 / 25 Jets as projections π π p φ K LO partons NLO partons parton shower hadron level Jet Def n Jet Def n Jet Def n Jet Def n jet 1 jet 2 jet 1 jet 2 jet 1 jet 2 jet 1 jet 2 Projection to jets provides “common” view of different event levels But projection is not unique: we must define what we mean by a jet Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 4 / 25 This talk 1. How are jets defined? 2. What pp physics is being done with jets? 3. What’s the forefront of research into jet techniques? 4. How about jets in heavy-ion collisions? Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 5 / 25 1. How are jets defined? Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 6 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance 1 diB = 2 pti 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a single particle 3. If it’s a diB call i a jet and remove it from list 4. Update all distances, go to step 1 Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance dmin is dij = 0.0001 p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance dmin is dij = 0.000197997 p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance dmin is dij = 0.000424056 p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4. Update all distances, go to step 1 0 0 1 2 3 4 y Gavin Salam (CERN/Princeton/Paris) Jets in SM and beyond PANIC, 28 July 2011 7 / 25 [1. Defining jets] The anti-kt jet algorithm Define “distance” between every pair of particles: [Cacciari, GPS & Soyez ’08] 2 1 ∆Rij 2 2 2 dij = ∆R = (yi − yj ) + (φi − φ ) max(p2 , p2 ) R2 ij j ti tj Define a single-particle distance dmin is dij = 0.000487076 p /GeV 1 t diB = 2 40 pti 30 1. Find the smallest of dij and diB 2. If it’s a dij , merge i and j into a 20 single particle 3. If it’s a diB call i a jet and remove it from list 10 4.